Physics: Chapter 4, 5, and 6 Concept Questions
A billiard ball is moving in the x-direction at 30.0 cm/s and strikes another billiard ball moving in the y-direction at 40.0 cm/s. As a result of the collision, the first ball moves at 50.0 cm/s, and the second ball stops. What is the change in kinetic energy of the system as a result of the collision?
0
A Hooke's law spring is compressed a distance d and is used to launch a particle of mass m vertically to a height h above its starting position. Under double the compression, the spring is now used to launch a particle of mass 2 m. How high does the second mass rise above its starting position?
2h
A Hooke's law spring is compressed a distance d and is used to launch a mass m vertically to a height h above its starting position. Under double the compression, the spring is now used to launch the mass. How high does the mass now rise above its starting position?
4h
The law of conservation of momentum is applicable to systems made up of objects described by which of the following?
All the above choices are valid.
Three satellites are launched into space connected together. Once in deep space, an explosive charge separates the three satellites and they move apart. The satellites each have different masses with m1 < m2 < m3. Which of the following statements is always true?
Although one or more of the above statements could be true in special cases, they are not always true.
It is late and Carlos is sliding down a rope from his third floor window to meet his friend Juan. As he slides down the rope faster and faster, he becomes frightened and grabs harder on the rope, increasing the tension in the rope. As soon as the upward tension in the rope becomes equal to his weight:
Carlos will continue down at a constant velocity.
Which of the following is an example of the type of force that acts at a distance?
Gravitational, Magnetic, and Electrical; All of the above
If during a given physical process the only force acting on an object is friction, which of the following must be assumed in regard to the object's kinetic energy?
It cannot be determined from the infor-mation given.
In a problem using energy considerations to solve for the speed of a ball thrown from the top of a building when it strikes the ground below, where should the potential energy have its zero value?
It doesn't matter since only differences in potential energy matter in solutions.
A crate of weight W is being pushed across a horizontal surface by a force directed at an angle of 20 below the horizontal. What is the magnitude of the normal force on the crate?
It is more than W.
Two masses m1 and m2, with m1 < m2, have momenta with equal magnitudes. How do their kinetic energies compare?
KE1 > KE2
The dimensional equivalent of the quantity impulse in terms of the fundamental quantities (mass, length, time) is which of the following?
MLT -1
The dimensional equivalence of the quantity "momentum" in terms of the fundamental quantities (mass, length, time) is:
MLT -1 .
The work done by static friction can be:
Negative, postive, zero; any of the above
When an object is dropped from a tower, what is the effect of the air resistance as it falls?
None of the above choices are valid.
Object 1 has twice the mass of Object 2. Both objects have the same kinetic energy. Which of the following statements is true?
Object 1 has a momentum of greater magnitude than Object 2.
Object 1 has twice the mass of Object 2. Each of the objects has the same magnitude of momentum. Which of the following statements is true?
One object has twice the kinetic energy of the other.
A block is projected with speed v across a horizontal surface and slides to a stop due to friction. The same block is then projected with the same speed v up an incline where is slides to a stop due to friction. In which case did the total mechanical energy of the block decrease the least? a.This problem cannot be solved since it was
The case on the inclined surface had the least decrease in total mechanical energy.
An object of mass m moving at speed v0 strikes an object of mass 2m which had been at rest. The first object bounces backward along its initial path at speed v0. Is this collision elastic, and if not, what is the change in kinetic energy of the system?
The kinetic energy increases by mv^2 .
Two objects, one less massive than the other, collide elastically and bounce back after the collision. If the two originally had velocities that were equal in size but opposite in direction, then which one will be moving faster after the collision?
The less massive one.
A 70-kg man is standing in a 20-kg boat. The man steps to the right thinking he is stepping out onto the dock. However, the following will actually happen (ignore the friction of the water or air on the boat or the man):
The man only moves a short distance to the right while the boat moves a larger distance to the left.
Three different mass projectiles are launched from the top of a building each at different angles of elevation. Each particle has the same initial kinetic energy. Which particle has the greatest speed just as it impacts with the ground?
The one with the lowest mass.
Two blocks are released from the top of a building. One falls straight down while the other slides down a smooth ramp. If all friction is ignored, which one is moving faster when it reaches the bottom?
They both will have the same speed.
If we know that a nonzero net force is acting on an object, which of the following must we assume regarding the object's condition? The object is:
being accelerated.
As a basketball player starts to jump for a rebound, he begins to move upward faster and faster until he leaves the floor. During this time that he is in contact with the floor, the force of the floor on his shoes is:
bigger than his weight.
The net force on an object is in the positive x-direction. Consider the following statements.
choose this answer if all the statements are true.
A billiard ball collides in an elastic head-on collision with a second stationary identical ball. After the collision which of the following conditions applies to the first ball?
comes to rest
As an object is lowered into a deep hole in the surface of the earth, which of the following must be assumed in regard to its potential energy?
decrease
Which of the following is an example of a nonconservative force?
friction
The maximum possible value for the coefficient of static friction is:
greater than 1.00.
A Hooke's law spring is compressed a distance d and is used to launch a mass m vertically to a height h above its starting position. Under the same compression d, the spring is now used to launch a mass of 2m. How high does this second mass rise?
h/2
A 5-kg object is moving to the right at 4 m/s and collides with another object moving to the left at 5 m/s. The objects collide and stick together. After the collision, the combined object:
has less kinetic energy than the system had before the collision.
A 5-kg object is moving to the right at 4 m/s and collides with a 4-kg object moving to the left at 5 m/s. The objects collide and stick together. After the collision, the combined object:
has no kinetic energy.
A student has to work the following problem: A block is being pulled along at constant speed on a horizontal surface a distance d by a rope supplying a force F at an angle of elevation ș. The surface has a frictional force acting during this motion. How much work was done by friction during this motion? The student calculates the value to be -Fdsinș. How does this value compare to the correct value?
he answer cannot be found until it is known whether ș is greater than, less than, or equal to 45°.
What condition must apply to a system's state of motion for it to be regarded as an inertial frame of reference?
in constant velocity
A force of 5.0 N is applied to a 20-kg mass on a horizontal frictionless surface. As the speed of the mass increases at a constant acceleration, the power delivered to it by the force:
increases.
A block is launched up an incline plane. After going up the plane, it slides back down to its starting position. The coefficient of friction between the block and the plane is 0.3. The speed of the block when it reaches the starting position on the trip down:
is less than the launching speed.
A block is launched up an incline plane. After going up the plane, it slides back down to its starting position. The coefficient of friction between the block and the plane is 0.3. The time for the trip up the plane:
is less than the time for the trip down.
The unit of power, watt, is dimensionally the same as:
joule/second.
A valid unit for momentum is which of the following?
kg m/s
The units of impulse are equivalent to:
kg m/s
Which of the following is that form of energy associated with an object's motion?
kinetic
As a car skids with its wheels locked trying to stop on a road covered with ice and snow, the force of friction between the icy road and the tires will usually be:
less than the normal force of the road times the coefficient of static friction.
As I slide a box at constant speed up a frictionless slope, pulling parallel to the slope, the tension in the rope will be:
less than the weight of the box.
Two objects, A and B, are placed on an inclined plane that can be rotated to different angles of elevation. A starts to slide at twice the angle of elevation that B starts sliding. The respective coefficients for static friction for A and B are mA and mB. Choose the last answer that is correct.
mA > mB
In a two-body collision, if the momentum of the system is conserved, then which of the following best describes the kinetic energy after the collision?
may also be conserved
A box of mass m is placed on an incline with angle of inclination q. The box does not slide. The magnitude of the frictional force in this case is:
mg sin q.
The impulse experienced by a body is equivalent to its change in:
momentum
If a two-body collision is not head-on, then we may always assume that:
momentum is conserved.
In a two-body collision, if the kinetic energy of the system is conserved, then which of the following best describes the momentum after the collision?
must also be conserved
The unit of work, joule, is dimensionally the same as:
newton-meter.
If the momentum of an object is tripled, its kinetic energy will change by what factor?
nine
Two particles collide, one of them initially being at rest. Is it possible for both particles to be at rest after the collision?
no
Which of the following is that form of energy associated with an object's location in a conservative force field?
potential
The rate at which work is done is equivalent to which of the following?
power
A lump of clay is thrown at a wall. A rubber ball of identical mass is thrown with the same speed toward the same wall. Which statement is true?
the ball experiences a greater change in momentum than the clay.
A thrown stone hits a window, but doesn't break it. Instead it reverses direction and ends up on the ground below the window. In this case, we know:
the force of the stone on the glass = the force of the glass on the stone.
A tennis ball is held above and in contact with a basketball, and then both are simultaneously dropped. The tennis ball bounces off the basketball at a fairly high speed. This is because:
the massive basketball transfers momentum to the lighter tennis ball.
In a partially elastic collision between two objects with unequal mass:
the momentum of one will increase by the amount that the momentum of the other decreases.
Which of the following expresses a principle, which was initially stated by Galileo and was later incorporated into Newton's laws of motion?
the natural condition for a moving object is to remain in motion.
If we know an object is moving at constant velocity, we may assume:
the net force acting on the object is zero.
As a car goes up a hill, there is a force of friction between the road and the tires rolling on the road. The maximum force of friction is equal to:
the normal force of the road times the coefficient of static friction.
A box is to be moved across a level surface. A force of magnitude 200 N may be applied at an angle of 30 below the horizontal to push the box or at an angle of 30 above the horizontal to pull the box, either application sufficient to overcome friction and move the box. Which application will cause the box to have the greater acceleration?
the one above the horizontal
Three different mass projectiles are launched from the top of a building each at different angles of elevation. Each particle has the same initial kinetic energy. Which particle has the greatest kinetic energy just as it impacts with the ground?
the one with the highest mass.
When a collision is perfectly inelastic, then:
the participants stick together.
A billiard ball collides in an elastic head-on collision with a second identical ball. What is the kinetic energy of the system after the collision compared to that before collision?
the same as
In an automobile collision, how does an airbag lessen the blow to the passenger? Assume as a result of the collision, the passenger stops.
the stopping impulse is the same for either the hard objects or the airbag. Unlike the windshield or dashboard, the air bag gives some increasing the time for the slowing process and thus decreasing the average force on the passenger.
If a glass of water is on a table with a piece of paper under it, it is relatively easy to pull the paper out without disturbing the glass very much if the pull is done very quickly. This is because, with a quick pull:
the time for the pull will be less.
A moderate force will break an egg. However, an egg dropped on the road usually breaks, while one dropped on the grass usually doesn't break. This is because for the egg dropped on the grass:
the time interval for stopping is greater.
In a system with two moving objects, when a collision occurs between the objects:
the total momentum is always conserved.
Kaitlin uses a bat to hit a thrown baseball. She knocks the ball back in the direction from which it came in a partially inelastic collision. The bat, which is heavier than the baseball, continues to move in the same direction after the hit as Kaitlin "follows through." Is the ball moving faster before or after it was hit?
there is insufficient information to answer this problem.
The statement by Newton that "for every action there is an opposite but equal reaction" is regarded as which of his laws of motion?
third
The kinetic energy of an object is quadrupled. Its momentum will change by what factor?
two
Two masses m1 and m2, with m1 = 3 m2, undergo a head-on elastic collision. If the particles were approaching with speed v before the collision, with what speed are they moving apart after collision?
v
The quantity of work equal to one joule is also equivalent to which of the following?
watts x sec
In the terminology a 500-N block, the 500-N refers to the block's:
weight.
The area under the force vs. displacement curve represents:
work.
Is it possible for the total mechanical energy of a moving particle to be negative?
yes
As a car moves forward on a level road at constant velocity, the net force acting on the tires is:
zero.
