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physics
college physics a strategic approach 2nd
College Physics A Strategic Approach 2nd Edition Randall D. Knight, Brian Jones, Stuart Field - Solutions
Density is the ratio of an object's mass to its volume. Would you expect density to be a vector or a scalar quantity? Explain.
Which of the following motions is described by the motion diagram of Figure Q 1.21?A. An ice skater gliding across the ice. B. An airplane braking to a stop after landing. C. A car pulling away from a stop sign. D. A pool ball bouncing off a cushion and reversing direction. FIGURE Q1.21 20 01
A bird flies 3.0 km due west and then 2.0 km due north. What is the magnitude of the bird's displacement? A. 2.0 km C. 3.6 km B. 3.0 km D. 5.0 km
The Empire State Building has a height of 1250 ft. Express this height in meters, giving your result in scientific notation with three significant figures.
A bird flies 3.0 km due west and then 2.0 km due north. Another bird flies 2.0 km due west and 3.0 km due north. What is the angle between the net displacement vectors for the two birds?A. 23° B. 34°C. 56°D. 90°
A woman walks briskly at 2.00 m/s. How much time will it take her to walk one mile?A. 8.30 min B. 13.4 min C. 21.7 min D. 30.0 min
Compute 3.24 m + 0.532 m to the correct number of significant figures. A. 3.7 m B. 3.77 m C. 3.772 m D. 3.7720 m
A rectangle has length 3.24 m and height 0.532 m. To the correct number of significant figures, what is its area?A. 1.72 m2 B. 1.723 m2 C. 1.7236 m2D. 1.72368 m2
Carol and Robin share a house. To get to work, Carol walks north 2.0 km while Robin drives west 7.5 km. How far apart are their workplaces?
Joe and Max shake hands and say goodbye. Joe walks east 0.55 km to a coffee shop, and Max flags a cab and rides north 3.25 km to a bookstore. How far apart are their destinations?
A city has streets laid out in a square grid, with each block 135 m long. If you drive north for three blocks, then west for two blocks, how far are you from your starting point?
A butterfly flies from the top of a tree in the center of a garden to rest on top of a red flower at the garden's edge. The tree is 8.0 m taller than the flower, and the garden is 12 m wide. Determine the magnitude of the butterfly's displacement.
A garden has a circular path of radius 50 m. John starts at the easternmost point on this path, then walks counterclockwise around the path until he is at its southernmost point. What is John's displacement? Use the (magnitude, direction) notation for your answer.
Migrating geese tend to travel in straight-line paths at approximately constant speed. A goose flies 32 km south, then turns to fly 20 km west. How far is the goose from its original position?
A ball on a porch rolls 60 cm to the porch's edge, drops 40 cm, continues rolling on the grass, and eventually stops 80 cm from the porch's edge. What is the magnitude of the ball's net dis- placement, in centimeters?
A kicker punts a football from the very center of the field to the sideline 43 yards downfield. What is the net displacement of the ball? (A football field is 53 yards wide.)
Joseph watches the roadside mile markers during a long car trip on an interstate highway. He notices that at 10:45 A.M. they are passing a marker labeled 101, and at 11:00 A.M. the car reaches marker 119. What is the car's speed, in mph?
Alberta is going to have dinner at her grandmother's house, but she is running a bit behind schedule. As she gets onto the highway, she knows that she must exit the highway within 45 min if she is not going to arrive late. Her exit is 32 mi away. What is the slowest speed at which she could drive
The end of Hubbard Glacier in Alaska advances by an average of 105 feet per year. What is the speed of advance of the glacier in m/s?
The earth completes a circular orbit around the sun in one year. The orbit has a radius of 93,000,000 miles. What is the speed of the earth around the sun in m/s? Report your result using scientific notation.
Shannon decides to check the accuracy of her speedometer. She adjusts her speed to read exactly 70 mph on her speedometer and holds this steady, measuring the time between successive mile markers separated by exactly 1.00 mile. If she measures a time of 54 s, is her speedometer accurate? If not, is
Your brain communicates with your body using nerve impulses, electrical signals propagated along axons. Axons come in two varieties: insulated axons with a sheath made of myelin, and uninsulated axons with no such sheath. Myelinated (sheathed) axons conduct nerve impulses much faster than
Satellite data taken several times per hour on a particular albatross showed travel of 1200 km over a time of 1.4 days. a. Given these data, what was the bird's average speed in mph? b. Data on the bird's position were recorded only intermittently. Explain how this means that the bird's actual
In 2003, the population of the United States was 291 million people. The per-capita income was $31,459. What was the total income of everyone in the United States? Express your answer in scientific notation, with the correct number of significant figures.
The sun is 30° above the horizon. It makes a 52-m-long shadow of a tall tree. How high is the tree?
A large passenger aircraft accelerates down the runway for a distance of 3000 m before leaving the ground. It then climbs at a steady 3.0 angle. After the plane has traveled 3000 m along this new trajectory,(a) How high is it,(b) How far horizontally is it, from its initial position?
Starting from its nest, an eagle flies at constant speed for 3.0 min due east, then 4.0 min due north. From there the eagle flies directly to its nest at the same speed. How long is the eagle in the air?
John walks 1.00 km north, then turns right and walks 1.00 km east. His speed is 1.50 m/s during the entire stroll. a. What is the magnitude of his displacement, from beginning to end? b. If Jane starts at the same time and place as John, but walks in a straight line to the endpoint of John's
For each motion diagram in Figure P2.2, determine the sign (positive or negative) of the position and the velocity.Data in Figure P2.2 (a) 0 X (b) (c)
A person gets in an elevator on the ground floor and rides it to the top floor of a building. Sketch a velocity-versus-time graph for this motion.
Write a short description of the motion of a real object for which Figure P2.3 would be a realistic position-versus-time graph. x (m) 300 200- 100 0 200 FIGURE P2.3 400 -t (s) 600
Write a short description of the motion of a real object for which Figure P2.4 would be a realistic position-versus-time graph. x (mi) 40 20 0 -20- 2 3 درا FIGURE P2.4 5 1 (h)
You are driving down the road at a constant speed. Another car going a bit faster catches up with you and passes you. Draw a position graph for both vehicles on the same set of axes, and note the point on the graph where the other vehicle passes you.
The position graph of Figure P2.5 shows a dog slowly. sneaking up on a squirrel, then putting on a burst of speed. a. For how many seconds does the dog move at the slower speed? b. Draw the dog's velocity-versus-time graph. Include a numerical scale on both axes. x (m) 6 4 2 0+ 0 FIGURE
A car is traveling north. Can its acceleration vector ever point south? Explain.
The position graph of Figure P2.6 represents the motion of a ball being rolled back and forth by two children. a. At what positions are the two children sitting? b. Draw the ball's velocity-versus-time graph. Include a numerical scale on both axes. FIGURE P2.6 x
Certain animals are capable of running at great speeds; other animals are capable of tremendous accelerations. Speculate on which would be more beneficial to a predator-large maximum speed or large acceleration.
Figure Q2.9 shows an object's position-versus-time graph. The letters A to E correspond to various segments of the motion in which the graph has constant slope.a. Write a realistic motion short story for an object that would have this position graph. b. In which segment(s) is the object at rest?c.
A bicyclist has the position-versus-time graph shown in Figure P2.9. What is the bicyclist's velocity at t = 10 s, at t = 25 s, and at t = 35 s? FIGURE P2.9 x (m) 100 50 0 10 20 30 40 -1 (s)
Figure Q2.10 shows the position graph for an object moving along the horizontal axis.Data in Figure Q2.10a. Write a realistic motion short story for an object that would have this position graph. b. Draw the corresponding velocity graph. X
Figure Q2.11 shows the position- versus-time graphs for two objects, A and B, that are moving along the same axis. FIGURE Q2.11a. At the instant t = 1 s, is the speed of A greater than, less than, or equal to the speed of B? Explain.b. Do objects A and B ever have the same speed? If so, at what
In college softball, the distance from the pitcher's mound to the batter is 43 feet. If the ball leaves the bat at 100 mph, how much time elapses between the hit and the ball reaching the pitcher?
Figure Q2.12 shows a position- versus-time graph. At which lettered point or points is the object.Figure Q2.12a. Moving the fastest? b. Moving to the left? c. Speeding up? d. Slowing down? e. Turning around? A B D E F
Figure Q2.13 is the velocity-versus-time graph for an object moving along the x-axis.a. During which segment(s) is the velocity constant? b. During which segment(s) is the object speeding up? c. During which segment(s) is the object slowing down? d. During which segment(s) is the object standing
A car traveling at velocity v takes distance d to stop after the brakes are applied. What is the stopping distance if the car is initially traveling at velocity 2v? Assume that the acceleration due to the braking is the same in both cases.
Figure Q2.17 shows an object's position-versus-time graph. What is the velocity of the object at t = 6 s?A. 0.67 m/s B. 0.83 m/s C. 3.3 m/s D. 4.2 m/s E. 25 m/s x (m) 40 30- 20 10- 0- 5 FIGURE Q2.17 -1 (s) 10
While running a marathon, a long-distance runner uses a stopwatch to time herself over a distance of 100 m. She finds that she runs this distance in 18 s. Answer the following by considering ratios, without computing her velocity. a. If she maintains her speed, how much time will it take her to
A somewhat idealized graph of the speed of the blood in the ascending aorta during one beat of the heart appears as in Figure P2.18.a. Approximately how far, in cm, does the blood move during one beat? b. Assume similar data for the motion of the blood in your aorta. Estimate how many beats of the
The following options describe the motion of four cars A-D. Which car has the largest acceleration?A. Goes from 0 m/s to 10 m/s in 5.0 s B. Goes from 0 m/s to 5.0 m/s in 2.0 s C. Goes from 0 m/s to 20 m/s in 7.0 s D. Goes from 0 m/s to 3.0 m/s in 1.0 s
A car starts from xi = 10 m at ti = 0 s and moves with the velocity graph shown in Figure P2.19. a. What is the object's position at t = 2 s, 3 s, and 4 s?b. Does this car ever change direction on? If so, at what time? v (m/s) 12- 8 0 FIGURE P2.19 -~ 2 4 -1 (s)
A car is traveling at vx 20 m/s. The driver applies the brakes, and the car slows with ax = -4.0 m/s2. What is the stopping distance? A. 5.0 m B. 25 m C. 40 m D. 50 m
Figure P2.20 shows a graph of actual position-versus-time data for a particular type of drag racer known as a "funny car." Figure P2.20a. Estimate the car's velocity at 2.0 s. b. Estimate the car's velocity at 4.0 s. x (m) 400 300 200 100 0- 0 N. 2 6 -1 (8)
Velocity-versus-time graphs for three drag racers are shown in Figure Q2.20. At t =5.0 s, which car has traveled the furthest?A. Andy B. Betty C. Carl D. All have traveled the same distance. v, (m/s) 40- +1 (8) 0 Andy 5.0 FIGURE Q2.20 v, (m/s) 40- 0- 0 +1(s) Betty 5.0 v
Ball 1 is thrown straight up in the air and, at the same instant, ball 2 is released from rest and allowed to fall. Which velocity graph in Figure Q2.22 best represents the motion of the two balls?Figure Q2.22 A. C. 2 2 B. V D. V 2 2 1 1
For each motion diagram shown earlier in Figure P2.2, determine the sign (positive or negative) of the acceleration.Figure P2.2, (a) 0 X (b) 0 (c)
Figure P2.18 showed data for the speed of blood in the aorta. Determine the magnitude of the acceleration for both phases, speeding up and slowing down. v (m/s) 1.0 0.5- FIGURE P2.18 0 0.20 0.40 0.60
A car can go from 0 to 60 mph in 7.0 s. Assuming that it could maintain the same acceleration at higher speeds, how long would it take the car to go from 0 to 120 mph? A. 10 s B. 14 s C. 21 s D. 28 s
Figure P2.25 is a somewhat simplified velocity graph for Olympic sprinter Carl Lewis starting a 100 m dash. Estimate his acceleration during each of the intervals A, B, and C.Figure P2.25 v, (m/s) 12- 10 8 6 4 2 0- A 0 1 B 2 3 دیا -1 (s) 4
A car can go from 0 to 60 mph in 12 s. A second car is capable of twice the acceleration of the first car. Assuming that it could maintain the same acceleration at higher speeds, how much time will this second car take to go from 0 to 120 mph? A. 12 s B. 9.0 s C. 6.0 s D. 3.0 s
A Thomson's gazelle can reach a speed of 13 m/s in 3.0 s. A lion can reach a speed of 9.5 m/s in 1.0 s. A trout can reach a speed of 2.8 m/s in 0.12 s. Which animal has the largest acceleration?
When striking, the pike, a predatory fish, can accelerate from rest to a speed of 4.0 m/s in 0.11 s.a. What is the acceleration of the pike during this strike? b. How far does the pike move during this strike?
Light-rail passenger trains that provide transportation within and between cities are capable of modest accelerations. The magnitude of the maximum acceleration is typically 1.3 m/s2, but the driver will usually maintain a constant acceleration that is less than the maximum. A train travels through
Figure P2.32 shows a velocity-versus-time graph for a particle moving along the x-axis. At t = 0 s, assume that x = 0 m.a. What are the particle's position, velocity, and acceleration at t = 1.0 s? b. What are the particle's position, velocity, and acceleration at t = 3.0 s? v,
A small propeller airplane can comfortably achieve a high enough speed to take off on a runway that is 1/4 mile long. A large, fully loaded passenger jet has about the same acceleration from rest, but it needs to achieve twice the speed to take off. What is the minimum runway length that will serve?
A driver has a reaction time of 0.50 s, and the maximum deceleration of her car is 6.0 m/s2. She is driving at 20 m/s when suddenly she sees an obstacle in the road 50 m in front of her. Can she stop the car in time to avoid a collision?
Chameleons catch insects with their tongues, which they can rapidly extend to great lengths. In a typical strike, the chameleon's tongue accelerates at a remarkable 250 m/s2 for 20 ms, then travels at constant speed for another 30 ms. During this total time of 50 ms, 1/20 of a second, how far does
A light-rail train going from one station to the next on a straight section of track accelerates from rest at 1.1 m/s2 for 20 s. It then proceeds at constant speed for 1100 m before slowing down at 2.2 m/s2 until it stops at the station. a. What is the distance between the stations? b. How much
A simple model for a person running the 100 m dash is to assume the sprinter runs with constant acceleration until reaching top speed, then maintains that speed through the finish line. If a sprinter reaches his top speed of 11.2 m/s in 2.14 s, what will be his total time?
Ball bearings can be made by letting spherical drops of molten metal fall inside a tall tower-called a shot tower-and solidify as they fall. a. If a bearing needs 4.0 s to solidify enough for impact, how high must the tower be? b. What is the bearing's impact velocity?
A student at the top of a building of height h throws ball A straight upward with speed vo and throws ball B straight down- ward with the same initial speed. a. Compare the balls' accelerations, both direction and magnitude, immediately after they leave her hand. Is one acceleration larger than
Excellent human jumpers can leap straight up to a height of 110 cm off the ground. To reach this height, with what speed would a person need to leave the ground?
A football is kicked straight up into the air; it hits the ground 5.2 s later. a. What was the greatest height reached by the ball? Assume it is kicked from ground level. b. With what speed did it leave the kicker's foot?
In an action movie, the villain is rescued from the ocean by grabbing onto the ladder hanging from a helicopter. He is so intent on gripping the ladder that he lets go of his briefcase of counterfeit money when he is 130 m above the water. If the briefcase hits the water 6.0 s later, what was the
A rock climber stands on top of a 50-m-high cliff overhanging a pool of water. He throws two stones vertically downward 1.0 s apart and observes that they cause a single splash. The initial speed of the first stone was 2.0 m/s. a. How long after the release of the first stone does the second stone
A truck driver has a shipment of apples to deliver to a destination 440 miles away. The trip usually takes him 8 hours. Today he finds himself daydreaming and realizes 120 miles into his trip that he is running 15 minutes later than his usual pace at this point. At what speed must he drive for the
Does a real automobile have constant acceleration? Measured data for a Porsche 944 Turbo at maximum acceleration are as shown in the table. a. Convert the velocities to m/s, then make a graph of velocity versus time. Based on your graph, is the acceleration constant? Explain. b. Draw a smooth
When you sneeze, the air in your lungs accelerates from rest to approximately 150 km/h in about 0.50 seconds. a. What is the acceleration of the air in m/s2? b. What is this acceleration, in units of g?
People hoping to travel to other worlds are faced with huge challenges. One of the biggest is the time required for a journey. The nearest star is 4.1 x 1016 m away. Suppose you had a spacecraft that could accelerate at 1.0g for half a year, then continue at a constant speed. (This is far beyond
You are driving to the grocery store at 20 m/s. You are 110 m from an intersection when the traffic light turns red. Assume that your reaction time is 0.70 s and that your car brakes with constant acceleration. a. How far are you from the intersection when you begin to apply the brakes? b. What
When you blink your eye, the upper lid goes from rest with your eye open to completely covering your eye in a time of 0.024 s. a. Estimate the distance that the top lid of your eye moves during a blink. b. What is the acceleration of your eyelid? Assume it to be constant. c. What is your upper
A bush baby, an African primate, is capable of leaping vertically to the remarkable height of 2.3 m. To jump this high, the bush baby accelerates over a distance of 0.16 m while rapidly extending its legs. The acceleration during the jump is approximately constant. What is the acceleration in m/s2
When jumping, a flea reaches a takeoff speed of 1.0 m/s over a distance of 0.50 mm.a. What is the flea's acceleration during the jump phase? b. How long does the acceleration phase last? c. If the flea jumps straight up, how high will it go? (Ignore air resistance for this problem; in reality,
Certain insects can achieve seemingly impossible accelerations while jumping. The click beetle accelerates at an astonishing 400g over a distance of 0.60 cm as it rapidly bends its thorax, making the "click" that gives it its name.a. Assuming the beetle jumps straight up, at what speed does it
Divers compete by diving into a 3.0-m-deep pool from a platform 10 m above the water. What is the magnitude of the minimum acceleration in the water needed to keep a diver from hitting the bottom of the pool? Assume the acceleration is constant.
A juggler throws a ball straight up into the air with a speed of 10 m/s. With what speed would she need to throw a second ball half a second later, starting from the same position as the first. in order to hit the first ball at the top of its trajectory?
A car starts from rest at a stop sign. It accelerates at 2.0 m/s2 for 6.0 seconds, coasts for 2.0 s, and then slows down at a rate of 1.5 m/s2 for the next stop sign. How far apart are the stop signs?
Heather and Jerry are standing on a bridge 50 m above a river. Heather throws a rock straight down with a speed of 20 m/s. Jerry, at exactly the same instant of time, throws a rock straight up with the same speed. Ignore air resistance. a. How much time elapses between the first splash and the
A piano has been pushed to the top of the ramp at the back of a moving van. The workers think it is safe, but as they walk away, it begins to roll down the ramp. If the back of the truck is 1.0 m above the ground and the ramp is inclined at 20°, how much time do the workers have to get to the
A ball is fired from a cannon at point 1 and follows the trajectory shown in Figure Q3.21. Air resistance may be neglected. Five possible vectors are also shown in the figure; the letter E represents the zero vector. Which vector best represents.a. The ball's velocity at position 2? b. The ball's
Starting from rest, several toy cars roll down ramps of differing lengths and angles. Rank them according to their speed at the bottom of the ramp, from slowest to fastest. Car A goes down a 10 m ramp inclined at 15°, car B goes down a 10 m ramp inclined at 20°, car C goes down an 8.0 m ramp
A ball thrown at an initial angle of 37.0° and initial velocity of 23.0 m/s reaches a maximum height h, as shown in Figure Q3.22. With what initial speed must a ball be thrown straight up to reach the same maximum height h?A. 13.8 m/s B. 17.3 m/s C. 18.4 m/sD. 23.0 m/s 23.0 m/s 37.0⁰ FIGURE
A cannon, elevated at 40° is fired at a wall 300 m away on level ground, as shown in Figure Q3.23. The initial speed of the cannonball is 89 m/s.a. How long does it take for the ball to hit the wall? A. 1.3 s B. 3.3 s C. 4.4 s D. 6.8 s E. 7.2 s b. At what height h does the ball hit the
A car drives horizontally off a 73-m-high cliff at a speed of 27 m/s. Ignore air resistance. a. How long will it take the car to hit the ground? A. 2.0 s B. 3.2 s C. 3.9 s D. 4.9 s E. 5.0 s b. How far from the base of the cliff will the car hit? A. 74 m B. 88 m C. 100 m D. 170 m E. 280 m
A plane has an airspeed of 200 mph. The pilot wishes to reach a destination 600 mi due east, but a wind is blowing at 50 mph in the direction 30° north of east. a. In what direction must the pilot head the plane in order to reach her destination? b. How long will the trip take?
A 1000 kg car traveling at a speed of 40 m/s skids to a halt on wet concrete where μk = 0.60. How long are the skid marks?
Eric has a mass of 60 kg. He is standing on a scale in an elevator that is accelerating downward at 1.7 m/s2. What is the approximate reading on the scale?A. ON B. 400 N C. 500 N D. 600 N
The two blocks in Figure Q5.28 are at rest on frictionless surfaces. What must be the mass of the right block in order that the two blocks remain stationary?A. 4.9 kg B. 6.1 kg C. 7.9 kgD. 9.8 kgE. 12 kg FIGURE Q5.28 10 kg 23° 40%
A 5.0-m-diameter merry-go-round is turning with a 4.0 s period. What is the speed of a child on the rim?
A 50 g ball of clay traveling at speed vi hits and sticks to a 1.0 kg block sitting at rest on a frictionless surface. a. What is the speed of the block after the collision? b. Show that the mechanical energy is not conserved in this collision. What percentage of the ball's initial kinetic energy
Jake hits a ball at a 600 angle from the horizontal. It is caught by Jim. Draw a motion diagram of the ball that shows velocity vectors rather than displacement vectors.This example is typical of how many problems in science and engineering are worded. The problem does not give a clear statement of
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