Questions and Answers of Physics Everyday Phenomena

A car traveling at a speed of 18 m/s (approximately 40 MPH) crashes into a solid concrete wall. The driver has a mass of 90 kg.a. What is the change in momentum of the driver as he comes to a stop?b.
Consider two cases in which the same ball is thrown against a wall with the same initial velocity. In case A, the ball sticks to the wall and does not bounce. In case B, the ball bounces back with
A bullet is fired into a block of wood sitting on a block of ice. The bullet has an initial velocity of 500 m/s and a mass of 0.005 kg. The wooden block has a mass of 1.2 kg and is initially at rest.
A fast ball thrown with a velocity of 40 m/s (approximately 90 MPH) is struck by a baseball bat, and a line drive comes back toward the pitcher with a velocity of 60 m/s. The ball is in contact with
A truck with a mass of 4000 kg traveling with a speed of 10 m/s collides at right angles with a car with a mass of 1500 kg traveling with a speed of 20 m/s.a. Sketch to proper scale and direction the
For the two vehicles in exercise 16:a. Sketch to scale the momentum vectors of the two vehicles prior to the collision.b. Add the two vectors on your sketch graphically Data From exercise 16A
A 4000-kg truck traveling with a velocity of 10 m/s due north collides head-on with a 1200-kg car traveling with a velocity of 20 m/s due south. The two vehicles stick together after the collision.a.
For the railroad cars in example box 7.4:a. What is the kinetic energy of car 5 before the collision?b. What is the kinetic energy of all five cars just after the collision?c. Is energy conserved in
A railroad car with a mass of 12 000 kg collides and couples with a second car of mass 18 000 kg that is initially at rest. The first car is moving with a speed of 12 m/s prior to the collision.a.
A rocket ship at rest in space gives a short blast of its engine, firing 50 kg of exhaust gas out the back end with an average velocity of 400 m/s. What is the change in momentum of the rocket during
A rifle with a mass of 1.2 kg fires a bullet with a mass of 6.0 g (0.006 kg). The bullet moves with a muzzle velocity of 600 m/s after the rifle is fired.a. What is the momentum of the bullet after
An ice skater with a mass of 80 kg pushes off against a second skater with a mass of 32 kg. Both skaters are initially at rest.a. What is the total momentum of the system after they push off?b. If
A fullback with a mass of 100 kg and a velocity of 3.5 m/s due west collides head-on with a defensive back with a mass of 80 kg and a velocity of 6 m/s due east.a. What is the initial momentum of
A ball traveling with an initial momentum of 4.0 kg·m/s bounces off a wall and comes back in the opposite direction with a momentum of - 3.5 kg·m/s.a. What is the change in momentum of the ball?b.
A ball traveling with an initial momentum of 2.5 kg·m/s bounces off a wall and comes back in the opposite direction with a momentum of - 2.5 kg·m/s.a. What is the change in momentum of the ball?b.
A 60-kg front-seat passenger in a car moving initially with a speed of 18 m/s (40 MPH) is brought to rest by an airbag in a time of 0.4 s.a. What is the impulse acting on the passenger?b. What is the
A ball experiences a change in momentum of 24 kg·m/s.a. What is the impulse acting on the ball?b. If the time of interaction is 0.15 s, what is the magnitude of the average force acting on the ball?
A 0.12-kg ball traveling with a speed of 40 m/s is brought to rest in a catcher’s mitt. What is the size of the impulse exerted by the mitt on the ball?
A force of 45 N acts on a ball for 0.2 s. If the ball is initially at rest:a. What is the impulse on the ball?b. What is the final momentum of the ball?
A bowling ball has a mass of 6 kg and a speed of 1.5 m/s. A baseball has a mass of 0.12 kg and a speed of 40 m/s. Which ball has the larger momentum?
What is the momentum of a 1200-kg car traveling with a speed of 27 m/s (60 MPH)?
An average force of 300 N acts for a time interval of 0.04 s on a golf ball.a. What is the magnitude of the impulse acting on the golf ball?b. What is the change in the golf ball’s momentum?
Suppose that the mass in question 26 is halfway between one of the extreme points of its motion and the center point. In this position, is the energy of the system kinetic energy, potential energy,
List the following lengths in descending order: kilometer, feet, mile, centimeter, inch. The conversion factors given on the inside front cover may be useful
List the following volumes in descending order: gallon, quart, liter, milliliter. The conversion factors given on the inside front cover may be useful.
A pirate map indicates that a treasure is buried 50 paces due east and 120 paces due north of a big rock. Will you know where to dig? Explain.
The width of a man’s hand was used as a common unit of length several hundred years ago. What are the advantages and disadvantages of using such a unit? Explain.
Which system of units, the metric system or English system, is used more widely throughout the world? Explain.
What are the advantages, if any, of continuing to use the English system of units in industry and commerce rather than converting to the metric system? Explain.
What are the primary advantages of the metric system of units over the older English system of units? Explain.
The distance that an object travels when it starts from rest and undergoes constant acceleration is one-half the acceleration multiplied by the square of the time. Invent your own symbols and express
Impulse is defined as the average force acting on an object multiplied by the time the force acts. If we let I represent impulse, F the average force, and t the time, is I F/t a correct way of
Suppose that you are told that speed is defined by the relationship s d/t, where s represents speed, d represents distance, and t represents time. State this relationship in words, using no
Based upon the descriptions provided in table 1.2, which subfields of physics are involved in explaining why an ice cube melts? Which subfields are involved in explaining how an airplane flies?
Based upon the brief descriptions provided in table 1.2, which subfield of physics would you say is involved in the explanation of rainbows? Which subfield is involved in describing how an acorn
Which of the three science fields: biology, chemistry, or physics, would you say is the most fundamental? Explain by describing in what sense one of these fields may be more fundamental than the
Suppose that a friend states the hypothesis that the color of socks that he wears on a given day, brown or black, will determine whether the stock market will go up or down. He can cite several
Suppose that your phone has not rung in several days, but a friend tells you he has tried to call. Develop two hypotheses that could explain why the phone has not rung and state how you would test
Suppose that your car will not start and you form the hypothesis that the battery is dead. How would you test this hypothesis? Explain.
Over the years, there have been several credible claims by experienced observers of sightings of Unidentified Flying Objects (UFOs). Despite this, scientists have shied away from taking up serious
Historians sometimes develop theories to explain observed patterns in the history of different countries. Are these theories testable in the same sense as a theory in physics? Explain.
A person claiming to have paranormal powers states that she can predict which card will come up next in a shuffled deck of cards simply by exercising her mental powers. Is this a testable claim?
If an air bag inflates too rapidly and firmly during a collision, it can sometimes do more harm than good in low velocity collisions. Explain using impulse and momentum ideas.
What is the advantage of an air bag in reducing injuries during collisions? Explain using impulse and momentum ideas.
What is the advantage of a padded dashboard compared to a rigid dashboard in reducing injuries during collisions? Explain using momentum and impulse ideas.
Is there an advantage to following through when hitting a baseball with a bat, thereby maintaining a longer contact between the bat and the ball? Explain.
If a ball bounces off a wall so that its velocity coming back has the same magnitude that it had prior to bouncing:a. Is there a change in the momentum of the ball? Explain.b. Is there an impulse
Are impulse and momentum the same thing? Explain.
Are impulse and force the same thing? Explain.
Is it possible for a baseball to have as large a momentum as a much more massive bowling ball? Explain.
Two forces produce equal impulses, but the second force acts for a time twice that of the first force. Which force, if either, is larger? Explain.
Does the length of time that a force acts on an object have any effect on the strength of the impulse produced? Explain.
Suppose you wish to compare the work done by pushing a box on rollers up a ramp to the work done if you lift the box straight up to the same final height.a. What work is required to lift a 100N box
A sled and rider with a total mass of 40 kg are perched at the top of a hill as pictured in the diagram. The top of this hill is 40 m above the low point in the path of the sled. A second hump in the
Suppose that a 200-g mass (0.20 kg) is oscillating at the end of a spring upon a horizontal surface that is essentially friction-free. The spring can be both stretched and compressed and has a spring
A slingshot consists of a rubber strap attached to a Y-shaped frame, with a small pouch at the center of the strap to hold a small rock or other projectiles. The rubber strap behaves much like a
As described in example box 6.2, a 100-kg crate is accelerated by a net force of 50 N applied for 4 s.a. What is the acceleration of the crate from Newton’s second law?b. If it starts from rest,
Suppose that two horizontal forces are acting upon a 0.25-kg wooden block as it moves across a laboratory table: a 5-N force pulling the block and a 2-N frictional force opposing the motion. The
The frequency of oscillation of a pendulum is 8 cycles/s. What is the period of oscillation?
The time required for one complete cycle of a mass oscillating at the end of a spring is 0.25 s. What is the frequency of oscillation?
A 200-g mass lying on a frictionless table is attached to a horizontal spring with a spring constant of 400 N/m. The spring is stretched a distance of 40 cm (0.40 m).a. What is the initial potential
A roller-coaster car has a potential energy of 450 000 J and a kinetic energy of 120 000 J at point A in its travel. At the low point of the ride, the potential energy is zero, and 50 000 J of work
At the low point in its swing, a pendulum bob with a mass of 0.2 kg has a velocity of 4 m/s.a. What is its kinetic energy at the low point?b. Ignoring air resistance, how high will the bob swing
Which requires more work: lifting a 2-kg rock to a height of 4 m without acceleration, or accelerating the same rock horizontally from rest to a speed of 10 m/s?
To stretch a spring a distance of 0.20 m, 40 J of work is done.a. What is the increase in potential energy of the spring?b. What is the value of the spring constant k of the spring?
A spring with a spring constant k of 40 N/m has stretched a distance of 20 cm (0.20 m) from its original unstretched position. What is the increase in potential energy of the spring?
A box with a mass of 5.0 kg is lifted (without acceleration) through a height of 2.0 m, in order to place it upon the shelf of a closet.a. What is the increase in potential energy of the box?b. How
A 0.4-kg ball has a velocity of 20 m/s.a. What is the kinetic energy of the ball?b. How much work would be required to stop the ball?
A net force of 60 N accelerates a 4-kg mass over a distance of 10 m.a. What is the work done by this net force?b. What is the increase in kinetic energy of the mass?
A force of 50 N is used to drag a crate 4 m across a floor. The force is directed at an angle upward from the crate so that the vertical component of the force is 30 N and the horizontal component is
A rope applies a horizontal force of 180 N to pull a crate a distance of 2 m across the floor. A frictional force of 60 N opposes this motion.a. What is the work done by the force applied by the
A force of 60 N used to push a chair across a room does 300 J of work. How far does the chair move in this process?
A woman does 160 J of work to move a table 4 m across the floor. What is the magnitude of the force that the woman applied to the table if this force is applied in the horizontal direction?
A horizontally directed force of 40 N is used to pull a box a distance of 2.5 m across a tabletop. How much work is done by the 40-N force?
A man pushes very hard for several seconds upon a heavy rock, but the rock does not budge. Has the man done any work on the rock? Explain.
If one pole-vaulter can run faster than another, will the faster runner have an advantage in the pole vault? Explain.
Is the elastic potential energy stored in the pole the only type of potential energy involved in pole-vaulting? Explain.
Suppose that a pulley system is used to lift a heavy crate, but the pulleys have rusted and there are frictional forces acting on the pulleys. Will the useful work output of this system be greater
Can work done by a frictional force ever increase the total mechanical energy of a system? (Consider the acceleration of an automobile.) Explain.
A sled is given a push at the top of a hill. Is it possible for the sled to cross a hump in the hill that is higher than its starting point under these circumstances? Explain.
Suppose that a mass is hanging vertically at the end of a spring. The mass is pulled downward and released to set it into oscillation. Is the potential energy of the system increased or decreased
A spring gun is loaded with a rubber dart, the gun is cocked, and then fired at a target on the ceiling. Describe the energy transformations that take place in this process.
A mass attached to a spring, which in turn is attached to a wall, is free to move on a friction-free horizontal surface. The mass is pulled back and then released.a. What form of energy is added to
A bird grabs a clam, carries it in its beak to a considerable height, and then drops it on a rock below, breaking the clam shell. Describe the energy conversions that take place in this process.
Suppose that we burn a barrel of oil just to warm our hands on a cold day.a. From the standpoint of physics, is energy conserved in this process? Explain.b. Why is this a bad idea from an economic or
A man commutes to work in a large sport utility vehicle (SUV).a. What energy transformations occur in this situation?b. Is mechanical energy conserved in this situation? Explain.c. Is energy of all
A sports car accelerates rapidly from a stop and “burns rubber.’’a. What energy transformations occur in this situation?b. Is energy conserved in this process? Explain.
Is the total mechanical energy conserved in the motion of a pendulum? Will it keep swinging forever? Explain.
For the pendulum in question 22 when the pendulum bob is halfway between the high point and the low point in its swing is the total energy kinetic energy, potential energy, on both? Explain.
A pendulum is pulled back from its equilibrium (center) position and then released.a. What form of energy is added to the system prior to its release? Explain.b. At what points in the motion of the
Suppose that the physics instructor pictured in figure 6.15 gives the bowling ball a push as she releases it. Will the ball return to the same point or will her chin be in danger? Explain.
When a bow and arrow are cocked, a force is applied to the string in order to pull it back. Is the energy of the system increased? Explain.
Which has the greater potential energy: a ball that is 10 feet above the ground, or one with the same mass that is 20 feet above the bottom of a nearby 50-foot-deep well? Explain.
Suppose that work is done on a large crate to tilt the crate so that it is balanced on one edge, as shown in the diagram, rather than sitting squarely on the floor as it was at first. Has the
Is it possible for a system to have energy if nothing is moving in the system? Explain.
When work is done to increase the potential energy of an object without increasing its kinetic energy, is the net force acting on the object greater than zero? Explain.
A box is moved from the floor up to a tabletop but gains no speed in the process. Is there work done on the box, and if so, what has happened to the energy added to the system?
Two balls of the same mass are accelerated by different net forces such that one ball gains a velocity twice that of the other ball in the process. Is the work done by the net force acting on the
If there is just one force acting on an object, does its work necessarily result in an increase in kinetic energy? Explain.
A child pulls a block across the floor with force applied by a horizontally held string. A smaller frictional force also acts upon the block, yielding a net force on the block that is smaller than

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