physics test 2
A person carries a mass of 10 kg and walks along the +x-axis for a distance of 100m with a constant velocity of 2 m/s. What is the work done by this person?
0 J
Refer to Fig. 5-4. What is the amount of work done by force as the object moves up the inclined plane?
0 J
A spring is characterized by a spring constant of 60. N/m. How much potential energy does it store, when stretched by 1.0 cm?
0.3 J
If both the mass and the velocity of a ball are tripled, the kinetic energy is increased by a factor of
27
A 42.0 kg block of ice slides down the plane incline 34.0° in Fig. 4-14. Assuming friction is negligible, what is the acceleration of the block down the incline?
5.48 m/s2
Car J moves twice as fast as car K, and car J has half the mass of car K. The kinetic energy of car J, compared to car K is
2 to 1
A car of mass M, traveling with a velocity V, strikes a parked station wagon, whose mass is 2M. The bumpers lock together in this head-on inelastic collision. What fraction of the initial kinetic energy is lost in this collision?
2/3
Two cardboard boxes full of books are in contact with each other on a table, as shown in Fig. 4-4. Box H has twice the mass of box G. If you push on box G with a horizontal force F, then box H will experience a net force of
2/3 F.
Which of the graphs in Fig. 5-1 illustrates Hooke's Law?
graph d
If you push a 4-kg mass with the same force that you push a 10-kg mass from rest, then
the 4-kg mass accelerates 2.5 times faster than the 10-kg mass.
You are standing in a moving bus, and you suddenly fall backward. You can imply from this that the bus'.
velocity increased.
Assuming negligible friction, what spring constant would be needed by the spring in a "B-B gun" to fire a 10. gram pellet to a height of 100 meters if the spring is initially compressed 10. cm?
20. N/cm
The following four forces act on a 4.00 kg object: F1 = 300 N east F2 = 700 N north F3 = 500 N west F4 = 600 N south What is the acceleration of the object?
224 N in a direction 26.6° north of west
A 60.0-kg mass person wishes to push a 120-kg mass box across a level floor. The coefficient of static friction between the person's shoes and the floor is 0.700. What is the maximum coefficient of static friction between the box and the floor such that the person can push horizontally on the box and cause it to start moving?
0.350
Refer to Fig. 5-8. How much work was required to bring the 1000-kg roller coaster from point P to rest at point Q at the top of the 50. m peak?
0.49 MJ
How much energy is needed to change the speed of a 1600 kg sport utility vehicle from 15.0 m/s to 40.0 m/s?
1.10 MJ
A ball, of mass 100. g, is dropped from a height of 12. m. Its momentum when it strikes the ground is
1.5 kg∙m/s.
A 60. gram toy rocket achieves a speed of 80. m/s after 3.0 s, when fired straight up. What is the average total force on the rocket during the 3 s?
1.6 N
Refer to Fig. 5-4. What is the amount of work done by force as the object moves up the inclined plane?
12.0 J
A skier, of mass 60. kg, pushes off the top of a frictionless hill with an initial speed of 4.0 m/s. How fast will she be moving after dropping 10. m in elevation?
15. m/s
Refer to Fig. 4-13. If the train has an acceleration of 5.50 m/ , then the tension force in the coupling between the middle car and the engine car is
16.5 kN.
Refer to Fig. 4-13. The wheels of the engine are pushing back with what force?
27.5 kN
Refer to Fig. 5-8. How fast must the coaster be moving at P in order to coast to a stop at Q?
31 m/s
Refer to Fig. 5-8. If the roller coaster leaves point Q from rest, how fast is it traveling at point R?
31 m/s
A 200-g mass attached to the end of a spring causes it to stretch 5.0 cm. If another 200-g mass is added to the spring, the potential energy of the spring will be
4 times as much.
A handball of mass 0.10 kg, traveling horizontally at 25. m/s, strikes a wall and rebounds at 19. m/s. What is the change in the momentum of the ball?
4.4 N-s
A golf club exerts an average force of 1000 N on a 0.045-kg golf ball which is initially at rest. The club is in contact with the ball for 1.8 ms. What is the speed of the golf ball as it leaves the tee?
40 m/s
A small bomb, of mass 10. kg, is moving toward the North with a velocity of 5.0 m/s. It explodes into three fragments: a 5.0 kg fragment moving West with a speed of 8.0 m/s; a 4.0 kg fragment moving East with a speed of 10. m/s; and a third fragment with a mass of 1.0 kg. What is the velocity of the third fragment? (Neglect air friction.)
40 m/s North
A 10. kg mass, hung onto a spring, causes the spring to stretch 2.0 cm. The spring constant is
49 N/cm
Stacy (S) and David (D) are having a tug-of-war by pulling on opposite ends of a 5.0 kg rope. Stacy pulls with a 15. N force. What is David's force if the rope accelerates toward Stacy at 2.0 m/ ?
5 N
Matthew pulls his little sister Sarah in a sled on an icy surface (assume no friction), with a force of 60.0 Newtons at an angle of 37.0° upward from the horizontal. If he pulls her a distance of 12.0 m, the work he does is
575 J
Car A (mass = 1000 kg) moves to the right along a level, straight road at a speed of 6.0 m/s. It collides directly with car B (mass = 200 kg) in a completely inelastic collision. What is the momentum after the collision if car B was initially at rest?
6.0 KN-s to the right
An object of mass 10.0 kg is initially at rest. A 100 N force causes it to move horizontally through a distance of 6.00 m. What is the change in the kinetic energy of this object?
600 J
A 2.0 kg mass moving to the East at a speed of 4.0 m/s collides head-on in an inelastic collision with a stationary 2.0 kg mass. How much kinetic energy is lost during this collision?
8.0 J
A 6.00-kg block is in contact with a 4.00-kg block on a frictionless surface as shown in Fig. 4-11. The 6.00-kg block is being pushed by a 20.0-N force toward the 4.00-kg block. What is the magnitude of the force of the 6.00-kg block on the 4.00-kg block?
8.00 N
See Fig. 6-1. After leaving the platform, the diver's momentum will be least at which point?
B
Two toy cars (16 kg and 2 kg) are released simultaneously on an inclined plane that makes an angle of 30° with the horizontal. Which statement best describes their acceleration after being released
Both cars accelerate at a rate of g sin(30°).
You and your friend want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do so. Compare the gravitational potential energy (U) of you and your friend, after you both reach the top, assuming that you and your friend have equal masses.
Both of you have the same amount of potential energy.
A book can slide down a frictionless hill at constant velocity.
False
In an inelastic collision, the initial kinetic energy is less than the final kinetic energy.
False
The impulse delivered to an object is equal to the change in the object's velocity.
False
The kinetic coefficient of friction is usually larger than the static coefficient of friction.
False
The work required to stretch a spring changes linearly with the amount of stretch.
False
Your mass on the moon will be about one-sixth of your mass on Earth.
False
You slam on the brakes of your car in a panic, and skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidded, under the same conditions?
It would have skidded 4 times farther.
Planning to elope with her boyfriend, Janice slides down a rope from her fourth story window. As she slides down the rope, she tightens harder on the rope which of course increases the tension in the rope. When the upward tension in the rope equals Janice's weight
Janice will continue down at constant speed.
A leaf falls from a tree. Compare its kinetic energy K to its potential energy U.
K increases, and U decreases.
King Kong falls from the top of the Empire State Building, through the air (air friction is present), to the ground below. How does his kinetic energy (K) just before striking the ground compare to his potential energy (U) at the top of the building?
K is less than U.
Work is a vector quantity.
false
A Ping-Pong ball moving East at a speed of 4 m/s collides with a stationary bowling ball. The Ping-Pong ball bounces back to the West, and the bowling ball moves very slowly to the East. Which object experiences the greater magnitude impulse during the collision?
Neither; both experienced the same magnitude impulse.
If you blow up a balloon, and then release it, the balloon will fly away as the air rushes out. This is an illustration of:
Newton's Third Law.
A container of water is lifted vertically 3.0 m, then returned to its original position. If the total weight is 30. N, how much work was done?
No work was done.
A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car.
The force of collision on the truck is equal to the force of collision on the car.
You try to pull an object by tugging on a rope attached to the object with a force . The object does not move at all. What does this imply
The inertia of the object prevents it from accelerating.
An object is moving with constant velocity in a straight line. Which of the following statements is true?
The net force on the object is zero
A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the magnitude of the average collision force is correct?
The small car and the truck experience the same average force.
A 16-kg fish is weighed with two spring scales, each of negligible weight, as shown in Fig. 4-2. What will be the readings on the scales?
The sum of the two readings will be 32 kg.
A force can be exerted on an object and yet do no work.
True
A force is required to keep an object moving along a horizontal line
True
In a one-dimensional elastic collision of two identical masses, the masses always exchange velocities.
True
In any elastic head-on collision, the relative speed of the two objects after the collision has the same magnitude (but opposite direction) as before the collision, no matter what the masses are.
True
Kinetic energy is a scalar quantity.
True
Momentum is conserved during a completely inelastic collision.
True
The acceleration of an object depends only on the net applied force
True
The acceleration of an object does not have to be in the same direction as the net force applied to it.
True
The mass of an object is fixed, but its weight varies from location to location.
True
The moon pulls on the Earth with one-sixth of the force of the Earth exerts on the moon.
True
You fall, while skiing, and one ski (of weight W) loosens and slides down an icy slope (assume no friction), which makes an angle θ with the horizontal. The force that pushes it down along the hill is
W sin θ.
You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.
Work up is -, and the work down is +.
Is it possible for a system to have negative potential energy?
Yes, since the choice of the zero of potential energy is arbitrary.
Suppose a bug spatters upon your windshield as you drive down the road. Which sustains the greater change of momentum?
both the same
A toolbox, of mass M, is resting on a flat board, as shown in Fig. 4-5. One end of the board is lifted up until the toolbox just starts to slide. The angle θ that the board makes with the horizontal, for this to occur, depends on the
coefficient of static friction, .
A decoration, of mass M, is suspended by a string from the ceiling inside an elevator. The elevator is traveling UPWARD with a constant speed. The tension in the string is
equal to Mg.
An arrow is shot straight up. At the top of its path, the net force acting on it is
equal to its weight.
Batter up! Your bat hits the ball pitched to you with a 1500-N instantaneous force. The ball hits the bat with an instantaneous force, whose magnitude is
exactly equal to 1500 N.
If the net work done on an object is positive, then the object's kinetic energy
increases
When a cannon fires a cannonball, the cannon will recoil backward because the
momentum of the cannonball and cannon is conserved.
You are standing in a moving bus, facing forward, and you suddenly move forward as the bus comes to an immediate stop. What force caused you to move forward?
no forces were responsible for your fall.
If you push twice as hard against a stationary brick wall, the amount of work you do
remains constant at zero.
Refer to Fig. 5-8. If the roller coaster leaves point Q from rest, what is its speed at point S (at the top of the 25. m peak) compared to its speed at point R?
sqrt 2
If you pitch a baseball with twice the kinetic energy you gave it in a previous pitch, the magnitude of its momentum is
sqrt as much
Two equal mass balls (one blue and the other gold) are dropped from the same height, and rebound off the floor. The blue ball rebounds to a higher position. Which ball is subjected to the greater magnitude impulse during its collision with the floor?
the blue ball
A brick and a feather fall to the Earth at their respective terminal velocities. Which object experiences the greater force of air friction?
the brick
When you sit on a chair, the reaction to your weight is
the chair pushing on you.
Automobile air bags reduce what during a collision?
the forces exerted upon the passenger
A 100 kg football linebacker moving at 2 m/s tackles head-on an 80 kg halfback running 3 m/s. Neglecting the effects due to digging in of cleats
the halfback will drive the linebacker backward.
To push a piece of heavy furniture across the carpet usually takes more force to get it moving than it takes to keep is moving. This is becaus
the static coefficient of friction is larger than the kinetic coefficient.
A child's toy is suspended from the ceiling by means of a string. The Earth pulls downward on the toy with its weight force of 8 N. If this is the "action force," what is the "reaction force"?
the toy pulling upward on the Earth with an 8-N force
Suppose several forces are acting upon a mass m. The in = m refers
the vector sum of all the forces.
Two identical masses are attached by a light string that passes over a small pulley, as shown in Fig. 4-3. The table and the pulley are frictionless. The masses are moving
with an acceleration less than g.
A 4.0 kg box of fruit slides 8.0 m down a ramp, inclined at 30.° from the horizontal. If the box slides at a constant velocity of 5.0 m/s, the work done by gravity is
zero
Work done by STATIC FRICTION is always
zero
