Physics Final Exam

When an object is solely under the influence of conservative forces, the sum of its kinetic and potential energies does not change.

true

A stock person at the local grocery store has a job consisting of the following five segments: (1) picking up boxes from the stockroom floor (2) accelerating to a comfortable speed (3) carrying the boxes to the display at constant speed (4) decelerating to a stop (5) lowering the boxes to the floor Which of the fives segments of the job does the stock person do positive work on the boxes?

1 and 2

If the mass of the earth and all objects on it were suddenly doubled but the size remained the same, the acceleration due to gravity at the surface would become

2 times what it is now

A satellite in a circular orbit of radius R around planet X has an orbital period T. If Planet X had one-fourth as much mass, the orbital period of this satellite in an orbit of the same radius would be

2T

A restoring force of magnitude F acts on a system with a displacement of magnitude x. In which of the following cases will the system undergo simple harmonic motion?

F proportional to x

Suppose that an object is moving with constant nonzero acceleration. What is an accurate statement concerning its motion?

In equal times its velocity changes by equal amounts.

A certain frictionless simple pendulum having a length L and mass M swings with period T. If both L and M are reduced to 1/4 of their original value, what is the new period?

T/2

Two objects, each of weight W, hang vertically by a spring scales. The pulleys and the strings attached to the objects have negligible weight, and there is no appreciable friction in the pulleys. The reading in each scale is

W

When a rigid body rotates about a fixed axis, all the points in the body have the same

angular acceleration

Two stones, one of mass m and the other of mass 2m, are thrown directly upward with the same velocity at the same time from ground level and feel no air resistance. What is true about the stones?

at its highest point, the heavier stone will have twice as much gravitational potential energy as the lighter one because its twice as heavy

Two identical balls are thrown directly upward, ball A at speed v and ball B at speed 2v, and they feel no air resistance. What is true about the balls?

ball B will go four times as high as ball A because it had four times the initial kinetic energy

In a perfectly ELASTIC collision between two perfectly rigid objects

both the momentum and the kinetic energy of the system are conserved

You are driving a late model convertible car at the 65 mph speed limit with its soft flexible roof closed up and the windows closed. You observe that the roof

bows inward

A piece of wood is floating in a bathtub. A second piece of wood sits on top of the first piece and does not touch the water. If the top piece is taken off and placed in the water, what happens to the water level in the tub?

it does not change

You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You can either catch the object or deflect the object back toward your friend (such that it moves away from you with the same speed as it was originally thrown). What should you do in order to maximize your speed on the skateboard?

deflect the ball

While an object is in projectile motion (with upward being positive) with no air resistance the horizontal component of its velocity remains constant and the vertical component of its acceleration is

equal to -g

If a force always acts parallel to an object's direction of motion, that force cannot change the objects kinetic energy.

false

If the acceleration of an object is negative, the object must be slowing down.

false

If two nonzero vectors point in the same direction, their dot product must be zero.

false

If two vectors are perpendicular to each other, their cross product must be zero.

false

As the speed of a moving fluid decreases, the pressure in the fluid

increases

If we double only the amplitude of a vibrating ideal mass-and-spring system, the mechanical energy of the system

increases by a factor 4

A very small round ball is located near a large solid sphere of uniform density. The force that the large sphere exerts on the ball

is exactly the same as it would be if all the mass of the sphere were concentrated at the center of the sphere

You slam on the breaks 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 identical conditions?

it would have skidded 4 times farther

Suppose that a car traveling to the west (the -x direction) begins to slow down as it approaches a traffic light. What is true concerning its acceleration in the x direction?

its acceleration is positive but its velocity is negative

For general projectile motion, when the projectile is at the highest point of its trajectory

its velocity is perpendicular to the acceleration

A box of mass m is pressed against (but is not attached to) an ideal spring of force constant K and negligible mass, compressing the spring a distance of x. After it is released, the box slides up a frictionless incline and eventually stops. If we repeat this but instead use a spring having force constant 2k

just as it as it moves free of the spring, the kinetic energy the box will be twice as great as before just as it moves free of the spring, the speed of the box will be root2 times as great as before the box will go up the incline twice as high as before

A ball drops some distance and loses 30 J of gravitational potential energy. Do NOT ignore air resistance. How much kinetic energy did the ball gain.

less than 30 J

Salt water is more dense than fresh water. A ship floats in both fresh water and salt water. Compared to the fresh water, the volume of salt water displaced by the ship

less than the volume of fresh water

A brick is resting on a rough incline. The friction force action on the brick along the incline is

less than the weight of the brick

Two men, Joel and Jerry, push against a wall. Jerry stops after 10 minutes, while Joel is able to push for 5 minutes longer. Compare the work they do.

neither of them does any work

You are standing in a moving bus, facing forward, and you suddenly move forward as the bus comes to an immediate stop. The force acting on you that causes you to move forward is

no forces were acting on you to cause you to move forward

If you triple the pressure on the surface of a can of water, the buoyant force on a stone placed in that water will

not

Suppose you are playing hockey on a new-age ice surface for which there is no friction between the ice and the hockey puck. You wind up and hit the puck as hard as you can. After the puck loses contact with your stick, the puck will

not slow down or speed up

A mass M is attached to an ideal massless spring. When this system is set in motion it has a period T. What is the period if the mass is doubled to 2M?

root2T

A solid sphere a solid cylinder, and a hollow pipe all have equal masses and radii and are of uniform density. If the three are released simultaneously at the top of an inclined plane and roll without slipping, which one will reach the bottom first?

solid sphere

A uniform solid cylinder, a uniform thin-walled hollow cylinder, and a uniform solid sphere are released at the same time at the top of an inclined ramp. They all roll without slipping. In what order do they reach the bottom of the ramp?

sphere, disk, hoop

A ball is thrown directly upward and experiences no air resistance. What about its motion is correct?

the acceleration is downward during the entire time the ball is in the air

Tensile stress is

the applied force per cross-sectional area

A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. During the collision

the force on the truck due to the collisions is exactly equal to the force on the car

Two objects, one of mass m and the other of mass 2m, are dropped from the top of a building. When they hit the ground

the heavier one will have twice the kinetic energy of the lighter one

A box of mass m is pressed against (but is not attached to) an ideal spring of force constant k and negligible mass, compressing the spring a distance x. After it is released, the box slides up a frictionless incline and eventually stops. if we repeat this with a box of mass 2m

the lighter box will go twice as high up the incline as the heavier box

A horizontal disk rotates about a vertical axis through its center. Point P is midway between the center and the rim of the disk, and point Q is on the rim. If the disk turns with constant angular velocity, what is true?

the linear acceleration of Q is twice as great as the linear acceleration of P Q is moving twice as fast as P

A shell explodes into two fragments, one fragment 25 times heavier than the other. If any gas from the explosion has negligible mass, then

the momentum change of the lighter fragment is exactly the same as the momentum change of the heavier fragment

In an INELASTIC collision between two objects

the momentum of the system is conserved but the kinetic energy of the system is not conserved

An object is moving forward with a constant velocity. What is true about this object?

the net force on the object is zero

Tensile strain is

the ratio of the change in length to the original length

A small car has a head-on collision with a large truck. What is true concerning the magnitude of the average force due to the collision is correct?

the small car and the truck experience the same average force

When you ride a bicycle, in what direction is the angular velocity of the wheels?

to your left

For an object in uniform circular motion, its velocity and acceleration vectors are always perpendicular to each other at every point in the path.

true

If a force always acts perpendicular to an object's direction of motion, that force cannot change the object's kinetic energy.

true

If the dot product of two nonzero vectors is zero, the vectors must be perpendicular to each other.

true

If the graph of the position as a function of time for an object is a horizontal line, that object cannot be accelerating.

true

As you are leaving a building, the door opens outward. If the hinges on the door are on your left, what is the direction of the angular velocity of the door as you open it?

up

The angular momentum of a system remains constant

when no torque acts on the system

The position x of an object varies with time t. For which of the following equations relating x and t is the motion of the object simple harmonic motion?

x= 9cos3t

If you set the cruise control of your car to a certain speed and take a turn, the speed of the car will remain the same. Is the car accelerating?

yes

Is it possible for a system to have negative potential energy?

yes, since the choice of the zero of potential energy is arbitrary

A stalled car is being pushed up a hill at constant velocity by three people. The net force on the car is

zero

If vector A and vector B are nonzero vectors for which A * B = 0, it must follow that

|A x B| = AB