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Fundamentals of Ethics for Scientists and Engineers 1st Edition Edmund G. Seebauer, Robert L. Barry - Solutions
In Figure, Misako is about to do a push-up. Her center of gravity lies directly above point P on the floor, which is 0.9 m from her feet and 0.6 m from her hands. If her mass is 54 kg, what is the force exerted by the floor on her hands?
Juan and Bettina are carrying a 60-kg block on a 4-m board as shown in Figure. The mass of the board is 10 kg. Since Juan spends most of his time reading cookbooks, whereas Bettina regularly does push-ups, they place the block 2.5 m from Juan and 1.5 m from Bettina. Find the force in Newton’s
A crutch is pressed against the sidewalk with a force Fc along its own direction as in Figure. This force is balanced by the normal force Fn and a frictional force fs.(a) Show that when the force of friction is at its maximum value, the coefficient of friction is related to the angle θ by μs
Each of the objects shown in figure is suspended from the ceiling by a thread attached to the point marked x on the object. Describe the orientation of each suspended object with a diagram.
A square plate is produced by welding together four smaller square plates, each of side a as shown in figure. Plate 1 weighs 40 N; plate 2, 60 N; plate 3, 30 N; and plate 4, 50 N. Find the center of gravity (xcg,ycg).
A uniform rectangular plate has a circular section of radius R cut out as shown in Figure. Find the center of gravity of the system
When the tree in front of his house was cut down to widen the road, Jay did not want it to go without ceremony, so he hauled out his electric guitar and amplifier. All that remained was a uniform 10-m log of mass 100 kg resting on two supports, waiting to be cut up and taken away the next day. One
Bubba uses a crowbar that is 1 m long to lift a heavy crate off the ground. The crowbar rests on a rigid fulcrum 10 cm from one end as shown in Figure.(a) If Bubba exerts a downward force of 600 N on one end of the crowbar, what is the upward force exerted on the crate by the other end?(b) The
Figure shows a 25-foot sloop. The mast is a uniform pole of 120 kg and is supported on the deck and held fore and aft by wires as shown. The tension in the forestay (wire leading to the bow) is 1000 N. Determine the tension in the back stay and the force that the deck exerts on the mast. Is there a
The sloop in figure is rigged slightly differently from the one in Problem 17. The mass of the mast is 150 kg and the tension in the forestay is again 1000 N. Find the tension in the backstay and the force that the deck exerts on the mast. Is there a tendency for the mast to slide forward or aft?
A 3-m board of mass 5 kg is hinged at one end. A force F is applied vertically at the other end to lift a 60-kg block, which rests on the board 80 cm from the hinge, as shown in Figure.(a) Find the magnitude of the force needed to hold the board stationary at q = 30o.(b) Find the force
A cylinder of weight W is supported by a frictionless trough formed by a plane inclined at 30o to the horizontal on the left and one inclined at 60o on the right as shown in Figure. Find the force exerted by each plane on the cylinder.
An 80-N weight is supported by a cable attached to a strut hinged at point A as in Figure. The strut is supported by a second cable under tension T2. The mass of the strut is negligible.(a) What are the three forces acting on the strut?(b) Show that the vertical component of the tension T2 must
A horizontal board 8.0 m long is used by pirates to make their victims walk the plank. A pirate of mass 105 kg stands on the shipboard end of the plank to prevent it from tipping. Find the maximum distance the plank can overhang for a 63-kg victim to be able to walk to the end if(a) The mass of the
A uniform 18-kg door that is 2.0 m high by 0.8 m wide is hung from two hinges that are 20 cm from the top and 20 cm from the bottom. If each hinge supports half the weight of the door, find the magnitude and direction of the horizontal components of the forces exerted by the two hinges on the door.
Lou is promoting the grand opening of Roswell’s, a new nightclub with an alien theme. One end of a uniform 100-kg beam, 10 m long, is hinged to a wall, and the other end sticks out horizontally over the dance floor. A cable connects to the beam 6 m from the wall, as in Figure. Lou sits at the
The diving board shown in Figure has a mass of 30 kg. Find the force on the supports when a 70-kg diver stands at the end of the diving board. Give the direction of each support force as a tension or a compression.
Find the force exerted on the strut by the hinge at A for the arrangement in Figure if (a) The strut is weightless, and (b) The strut weighs 20N.
Julie has been hired to help paint the trim of a building, but she is not convinced of the safety of the apparatus. A 5.0-m plank is suspended horizontally from the top of the building by ropes attached at each end. She knows from previous experience, however, that the ropes being used will break
A cylinder of mass M and radius R rolls against a step of height h as shown in Figure. When a horizontal force F is applied to the top of the cylinder, the cylinder remains at rest. (a) What is the normal force exerted by the floor on the cylinder? (b) What is the horizontal force exerted by the
A strong man holds one end of a 3-m rod of mass 5 kg at rest in a horizontal position. (a) What total force does the man exert on the rod? (b) What total torque does the man exert on the rod? (c) If you approximate the effort of the man with two forces that act in opposite directions and are
A large gate weighing 200 N is supported by hinges at the top and bottom and is further supported by a wire as shown in Figure. (a) What must the tension in the wire be for the force on the upper hinge to have no horizontal component? (b) What is the horizontal force on the lower hinge? (c) What
A uniform log with a mass of 100 kg, a length of 4 m, and a radius of 12 cm is held in an inclined position, as shown in Figure. The coefficient of static friction between the log and the horizontal surface is 0.6. The log is on the verge of slipping to the right. Find the tension in the support
A tall, uniform, rectangular block sits on an inclined plane as shown in Figure. A cord is attached to the top of the block to prevent it from falling down the incline. What is the maximum angle q for which the block will not slide on the incline? Let b/a be 4 and ms = 0.8.
A thin rail of length 10 m and mass 20 kg is supported at a 30o incline. One support is 2 m and the other is 6 m from the lower end of the rail. Friction prevents the rail from sliding off the supports. Find the force (magnitude and direction) exerted on the rail by each support.
A uniform cube of side a and mass M rests on a horizontal surface. A horizontal force F is applied to the top of the cube as in Figure. This force is not sufficient to move or tip the cube. (a) Show that the force of static friction exerted by the surface and the applied force constitute a couple,
Resolve each force in Problem 40 into its horizontal and vertical components, producing two couples. The algebraic sum of the two component couples equals the resultant couple. Use this result to find the perpendicular distance between the lines of action of the two forces.
Is it possible to climb a ladder placed against a wall where the ground is frictionless but the wall is not? Explain.
Romeo takes a uniform 10-m ladder and leans it against the smooth wall of the Capulet residence. The ladder’s mass is 22.0 kg, and the bottom rests on the ground 2.8 m from the wall. When Romeo, whose mass is 70 kg, gets 90% of the way to the top, the ladder begins to slip. What is the
A massless ladder of length L leans against a smooth wall making an angle q with the horizontal floor. The coefficient of friction between the ladder and the floor is μs. A man of mass M climbs the ladder. What height h can he reach before the ladder slips?
A uniform ladder of length L and mass m leans against a frictionless vertical wall with its lower end on the ground. It makes an angle of 60o with the horizontal ground. The coefficient of static friction between the ladder and ground is 0.45. If your mass is four times that of the ladder, how far
A ladder of mass m and length L leans against a frictionless, vertical wall making an angle θ with the horizontal. The center of mass is at a height h from the floor. A force F pulls horizontally against the ladder at the midpoint. Find the minimum coefficient of static friction ms for which the
A 900-N boy sits on top of a ladder of negligible weight that rests on a frictionless floor as in Figure. There is a cross brace halfway up the ladder. The angle at the apex is q = 30o.(a) What is the force exerted by the floor on each leg of the ladder?(b) Find the tension in the cross brace.
A ladder rests against a frictionless vertical wall. The coefficient of static friction between ladder and the floor is 0.3. What is the smallest angle at which the ladder will remain stationary?
Having failed in his first attempt, Romeo acquires a new ladder to try once again to get to Juliet’s window. This one has a length L and a weight of 200 N. He tries placing it on the other side of the window, where the coefficients of static friction are 0.4 between the ladder and the wall, and
A ladder leans against a large smooth sphere of radius R that is fixed in place on a horizontal surface. The ladder makes an angle of 60o with the horizontal surface and has a length 5R/2.(a) What is the force that the sphere exerts on the ladder?(b) What is the frictional force that prevents the
A 50-kg ball is suspended from a steel wire of length 5 m and radius 2 mm. By how much does the wire stretch?
Copper has a breaking stress of about 3 x 108 N/m2.(a) What is the maximum load that can be hung from a copper wire of diameter 0.42 mm?(b) If half this maximum load is hung from the copper wire, by what percentage of its length will it stretch?
A 4-kg mass is supported by a steel wire of diameter 0.6 mm and length 1.2 m. How much will this wire stretch under this load?
As a runner’s foot touches the ground, the shearing force acting on an 8-mm-thick sole is as shown in Figure. If the force of 25 N is distributed over an area of 15 cm2, find the angle of shear q shown, given that the shear modulus of the sole is 1.9 x 105 N/m2.
A steel wire of length 1.5 m and diameter 1 mm is joined to an aluminum wire of identical dimensions to make a composite wire of length 3.0 m. What is the length of the composite wire if it is used to support a mass of 5 kg?
A force F is applied to a long wire of length L and cross-sectional area A. Show that if the wire is considered to be a spring, the force constant k is given by k = AY/L and the energy stored in the wire is U = ½ F ∆L, where Y is Young’s modulus and ∆L is the amount the wire has stretched.
The steel E string of a violin is under a tension of 53 N. The diameter of the string is 0.20 mm, and its length under tension is 35.0 cm. Find(a) The unstretched length of this string, and(b) The work needed to stretch the string. (see Problem 58)
When a rubber strip with a cross section of 3 mm x 1.5 mm is suspended vertically and various masses are attached to it, a student obtains the following data for length versus load:(a) Find Young’s modulus for the rubber strip for small loads.(b) Find the energy stored in the strip when the load
A building is to be demolished by a 400-kg steel ball swinging on the end of a 30-m steel wire of diameter 5 cm hanging from a tall crane. As the ball is swung through an arc from side to side, the wire makes an angle of 50o with the vertical at the top of the swing. Find the amount by which the
A large mirror is hung from a nail as shown in Figure. The supporting steel wire has a diameter of 0.2 mm and an unstretched length of 1.7 m. The distance between the points of support at the top of the mirror’s frame is 1.5 m. The mass of the mirror is 2.4 kg. What is the distance between the
Two masses, M1 and M2, are supported by wires of equal length when unstretched. The wire supporting M1 is an aluminum wire 0.7 mm in diameter, and the one supporting M2 is a steel wire 0.5 mm in diameter. What is the ratio M1/M2 if the two wires stretch by the same amount?
A mass of 0.5 kg is attached to an aluminum wire having a diameter of 1.6 mm and an unstretched length of 0.7 m. The other end of the wire is fixed to a post. The mass rotates about the post in a horizontal plane at a rotational speed such that the angle between the wire and the horizontal is 5.0o.
It is apparent from Table 12-2 that the tensile strength of most materials is two to three orders of magnitude smaller than Young?s modulus. Consequently, these materials, e.g., aluminum, will break before the strain exceeds even 1%. For nylon, however, the tensile strength and Young?s modulus are
A 90-N board 12 m long rests on two supports, each 1 m from the end of the board. A 360-N block is placed on the board 3 m from one end as shown in Figure. Find the force exerted by each support on the board.
Figure shows a mobile consisting of four weights hanging on three rods of negligible mass. Find the value of each of the unknown weights if the mobile is to balance.
A block and tackle is used to support a mass of 120 kg as shown in Figure. (a) What is the tension in the rope? (b) What is the mechanical advantage of this device?
A plate in the shape of an equilateral triangle of mass M is suspended from one corner and a mass m is suspended from another corner. What should be the ratio m/M so that the base of the triangle makes an angle of 6.0o with the horizontal?
A standard six-sided pencil is placed on a paper pad (Figure). Find the minimum coefficient of static friction ms such that it rolls down rather than slides if the pad is inclined.
Having lost his job at the post office, Barry decides to explore the possibility that he might be a brilliant sculptor. Not one to start at the bottom, he borrows the money for a marble slab 3m x 1m x 1m. After loading the marble onto the back of his truck, he drives off with the slab resting on
Barry’s art exhibit contains many tiny marble sculptures placed around a central piece called “Politics.” The central piece consists of three identical bars, each of length L and mass m, joined as in Figure. Two bars form a fixed ^, and the third bar is suspended on a hinge. Asked to explain
In the 1996 Olympics, the Russian super-heavyweight weightlifter Andrei Chemerkin broke the world record with a lift of mass 260 kg. Suppose his grip was slightly asymmetrical as shown in Figure. Find the maximum mass of the barbell Chemerkin could have handled with a symmetrical grip, assuming
A balance scale has unequal arms. A 1.5-kg block appears to have a mass of 1.95 kg on the left pan of the scale (Figure). Find its apparent mass if the block is placed on the right pan.
A cube of mass M leans against a frictionless wall making an angle q with the floor as shown in Figure. Find the minimum coefficient of static friction ms between the cube and the floor that allows the cube to stay at rest.
Figure shows a steel meter stick hinged to a vertical wall and supported by a thin wire. The wire and meter stick make angles of 45o with the vertical. The mass of the meter stick is 5.0 kg. When a mass M = 10.0 kg is suspended from the midpoint of the meter stick, the tension T in the supporting
Figure shows a 20-kg ladder leaning against a frictionless wall and resting on a frictionless horizontal surface. To keep the ladder from slipping, the bottom of the ladder is tied to the wall with a thin wire; the tension in the wire is 29.4 N. The wire will break if the tension exceeds 200 N. (a)
Suppose that the bar hanging from the end of the T in Problem 78 is of a different length ℓ ≠ L, although its mass per unit length is the same as that of the bars of the T. Find the ratio L/ℓ such that θ = 75o.
A uniform cube can be moved along a horizontal plane either by pushing the cube so that it slips or by turning it over (“rolling”). What coefficient of kinetic friction mk between the cube and the floor makes both ways equal in terms of the work needed?
A tall, uniform, rectangular block sits on an inclined plane as shown in Figure. If ms = 0.4, does the block slide or fall over as the angle q is slowly increased?
A 360-kg mass is supported on a wire attached to a 15-m-long steel bar that is pivoted at a vertical wall and supported by a cable as shown in Figure. The mass of the bar is 85 kg. (a) With the cable attached to the bar 5.0 m from the lower end as shown, find the tension in the cable and the force
A thin rod 60 cm long is balanced 20 cm from one end when a mass of 2m + 2 g is at the end nearest the pivot and a mass of m at the opposite end (Figure a). Balance is again achieved if the mass 2m + 2 g is replaced by the mass m and no mass is placed at the other end (Figure b). Determine the mass
The planet Mars has two satellites, Phobos and Deimos, in nearly circular orbits. The orbit radii of Phobos and Deimos are 9.38 x 103 km and 23.46 x 103 km, respectively. The mass of Mars is 6.42 x 1023 kg, that of Phobos is 9.63 x 1015 kg, and that of Deimos is 1.93 x 1015 kg. Find the center of
When a picture is hung on a smooth vertical wall using a wire and a nail, as in Figure, the picture almost always tips slightly forward, i.e., the plane of the picture makes a small angle with the vertical. (a) Explain why pictures supported in this manner generally do not hang flush against the
Repeat Problem 76 is Barry is driving(a) Uphill on a road inclined at 10o with the horizontal or(b) Downhill on a road inclined at 10o with the horizontal.
If a train travels around a bend in the railbed too fast, the freight cars will tip over. Assume that the cargo portions of the freight cars are regular parallelepipeds of uniform density and 1.5 x 104 kg mass, 10 m long, 3.0 m high, and 2.20 m wide, and that their base is 0.65 m above the rails.
For balance, a tightrope walker uses a thin rod 8 m long and bowed in a circular arc shape. At each end of the rod is a lead mass of 20 kg. The tightrope walker whose mass is 58 kg and whose center of gravity is 0.90 m above the rope, holds the rod tightly at its center 0.65 m above the rope. What
A large crate weighing 4500 N rests on four 12-cm-high blocks on a horizontal surface (Figure). The crate is 2 m long, 1.2 m high and 1.2 m deep. You are asked to lift one end of the crate using a long steel bar. The coefficient of static friction between the blocks and the supporting surface is
Six identical bricks are stacked one on top of the other lengthwise and slightly offset to produce a stepped tower with the maximum offset that will still allow the tower to stand.(a) Starting from the top, give the maximum possible offset for each successive brick.(b) What is the total protrusion
A uniform sphere of radius R and mass M is held at rest on an inclined plane of angle q by a horizontal string, as shown in Figure. Let R = 20 cm, M = 3 kg, and q = 30o. (a) Find the tension in the string. (b) What is the normal force exerted on the sphere by the inclined plane? (c) What is the
The legs of a tripod make equal angles of 90o with each other at the apex, where they join together. A 100-kg block hangs from the apex. What are the compressional forces in the three legs?
Figure shows a 20-cm-long uniform beam resting on a cylinder of 4 cm radius. The mass of the beam is 5.0 kg, and that of the cylinder is 8.0 kg. The coefficient of friction between beam and cylinder is zero. (a) Find the forces that act on the beam and on the cylinder. (b) What must the minimum
Two solid smooth spheres of radius r are placed inside a cylinder of radius R as in Figure. The mass of each sphere is m. Find the force exerted by the bottom of the cylinder, the force exerted by the wall of the cylinder, and the force exerted by one sphere on the other.
A solid cube of side length a balanced atop a cylinder of diameter d is in unstable equilibrium if d > a (Figure). Determine the minimum value of d/a for which the cube is in stable equilibrium.
(Multiple choice)(1) True and False(a) ΣF = 0 is sufficient for static equilibrium to exist. (b) ΣF = 0 is necessary for static equilibrium to exist. (c) In static equilibrium, the net torque about any point is zero. (d) An object is in equilibrium only when there are no forces
A copper cylinder is 6 cm long and has a radius of 2 cm. Find its mass.
Find the mass of a lead sphere of radius 2 cm.
A solid oak door is 200 cm high, 75 cm wide, and 4 cm thick. How much does it weigh?
A 60-mL flask is filled with mercury at 0oC (Figure). When the temperature rises to 80oC, 1.47 g of mercury spills out of the flask. Assuming that the volume of the flask is constant, find the density of mercury at 80oC if its density at 0oC is 13,645kg/m3
Barometer readings are commonly given in inches of mercury. Find the pressure in inches of mercury equal to 101kPa.
The pressure on the surface of a lake is atmospheric pressure Pat = 101kPa.(a) At what depth is the pressure twice atmospheric pressure?(b) If the pressure at the top of a deep pool of mercury is Pat, at what depth is the pressure 2Pat?
Find(a) The absolute pressure and(b) The gauge pressure at the bottom of a swimming pool of depth 5.0 m.
When a woman in high heels takes a step, she momentarily places her entire weight on one heel of her shoe, which has a radius of 0.4 cm. If her mass is 56 kg, what is the pressure exerted on the floor by her heel?
A hydraulic lift is used to raise an automobile of mass 1500 kg. The radius of the shaft of the lift is 8 cm and that of the piston is 1 cm. How much force must be applied to the piston to raise the automobile?
Blood flows into the aorta through a circular opening of radius 0.9 cm. If the blood pressure is 120torr, how much force must be exerted by the heart?
What pressure is required to reduce the volume of 1 kg of water from 1.00 L to 0.99 L?
A 1500-kg car rests on four tires, each of which is inflated to a gauge pressure of 200kPa. What is the area of contact of each tire with the road, if the four tires support the weight equally?
In the seventeenth century, Pascal performed the experiment shown in figure. A wine barrel filled with water was coupled to a long tube. Water was added to the tube until the barrel burst. (a) If the radius of the lid was 20 cm and the height of the water in the tube was 12 m, calculate the force
Blood plasma flows from a bag through a tube into a patient’s vein, where the blood pressure is 12 mmHg. The specific gravity of blood plasma at 37oC is 1.03. What is the minimum elevation the bag must have so that the pressure of the plasma as it flows into the vein is at least 12 mmHg?
Many people have imagined that if they were to float the top of a flexible snorkel tube out of the water, they would be able to breathe through it while walking underwater (Figure). However, they generally do not reckon with just how much water pressure opposes the expansion of the chest and the
In Example 13-3, a force of 147 N is applied to a small piston to lift a car that weighs 14,700 N. Demonstrate that this does not violate the law of conservation of mechanical energy by showing that, when the car is lifted some distance h, the work done by the force acting on the small piston
The volume of a cone of height h and base radius r is A conical vessel of height 25 cm resting on its base of radius 15 cm is filled with water.(a) Find the volume and weight of the water in the vessel.(b) Find the force exerted by the water on the base of the vessel. Explain how this force can be
Two objects are balanced as in figure. The objects have identical volumes but different masses. Will the equilibrium be disturbed if the entire system is completely immersed in water? Explain.
A 500-g piece of copper (specific gravity 9.0) is suspended from a spring scale and is submerged in water (Figure). What force does the spring scale read?
An object floats on water with 80% of its volume below the surface. The same object when placed in another liquid floats on that liquid with 72% of its volume below the surface. Determine the density of the object and the specific gravity of the liquid.
A 5-kg iron block is attached to a spring scale and is submerged in a fluid of unknown density. The spring scale reads 6.16 N. What is the density of the fluid?
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