Physics Test #2
A 2.00-kg ball has zero potential and kinetic energy. Maria drops the ball into a 10.0-m-deep well. After the ball comes to a stop in the mud, the sum of its potential and kinetic energy is:
-196 J
A horizontal force of 200 N is applied to a 55-kg cart across a 10-m level surface. If the cart accelerates at 2.0 m/s2, then what is the work done by the force of friction as it acts to retard the motion of the cart?
-900 J
A 100-kg box is placed on a ramp. As one end of the ramp is raised, the box begins to move downward just as the angle of inclination reaches 15°. What is the coefficient of static friction between box and ramp?
0.27
I drop a 60-g golf ball from 2.0 m high. It rebounds to 1.5 m. How much energy is lost?
0.29 J
A horizontal force of 750 N is needed to overcome the force of static friction between a level floor and a 250-kg crate. If g = 9.8 m/s2, what is the coefficient of static friction?
0.31
A cart of weight 20 N is accelerated across a level surface at 0.15 m/s2. What net force acts on the wagon? (g = 9.8 m/s2)
0.31 N
Dana uses a rope to pull a box that weighs 300 N across a level surface with constant velocity. The rope makes an angle of 30° above the horizontal and the tension in the rope is 100 N. What is the coefficient of friction?
0.35
Two blocks of masses 20 kg and 8 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8-kg mass is another light string, which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.5 m/s2 what is the tension in the connecting string between the blocks?
10 N
A 15.0-kg crate, initially at rest, slides down a ramp 2.0 m long and inclined at an angle of 20° with the horizontal. If there is no friction between ramp surface and crate, what is the kinetic energy of the crate at the bottom of the ramp? (g = 9.8 m/s2)
100 J
Two tug-of-war opponents each pull with a force of 100 N on opposite ends of a rope. What is the tension in the rope?
100 N
You tie a rope to a tree and you pull on the rope with a force of 100 N. What is the tension in the rope?
100 N
What is the kinetic energy of a 0.135-kg baseball thrown at 40.0 m/s (90.0 mph)?
108 J
A rock is thrown straight up with an initial velocity of 15.0 m/s. Ignore energy lost to air friction. How high will the rock rise?
11.5 m
A 7.00-kg bowling ball falls from a 2.00-m shelf. Just before hitting the floor, what will be its kinetic energy? (g = 9.80 m/s2 and assume air resistance is negligible)
137 J
An amount of work equal to 1.5 J is required to compress the spring in a spring gun. What is the "launch speed" of a 15 g marble?
14 m/s
A block of mass 5.00 kg rests on a horizontal surface where the coefficient of kinetic friction between the two is 0.200. A string attached to the block is pulled horizontally, resulting in a 2.00-m/s2 acceleration by the block. Find the tension in the string. (g = 9.80 m/s2)
19.8 N
Samantha pushes a 50-N crate up a ramp 25.0 m in length and inclined at 10 with the horizontal. What potential energy change does the crate experience?
220 J
Rita accelerates a 0.40-kg ball from rest to 9.0 m/s during the 0.15 s in which her foot is in contact with the ball. What average force does she apply to the ball during the kick?
24 N
A girl is using a rope to pull a box that weighs 300 N across a level surface with constant velocity. The rope makes an angle of 30° above the horizontal, and the tension in the rope is 100 N. What is the normal force of the floor on the box?
250 N
If both mass and velocity of a ball are tripled, the kinetic energy is increased by a factor of:
27
A 10.0-kg box starts at rest and slides 3.5 m down a ramp inclined at an angle of 10° with the horizontal. If there is no friction between the ramp surface and crate, what is the velocity of the crate at the bottom of the ramp? (g = 9.8 m/s2)
3.5 m/s
By how much is the energy stored in a Hooke's law spring increased when its stretch is increased from 8.00 cm to 16.0 cm?
300 %
A professional skier reaches a speed of 56 m/s on a 30° ski slope. Ignoring friction, what was the minimum distance along the slope the skier would have had to travel, starting from rest?
320 m
A sled weighs 100 N. It is held in place on a frictionless 20° slope by a rope attached to a stake at the top; the rope is parallel to the slope. Find the tension in the rope.
34 N
Doug hits a hockey puck, giving it an initial velocity of 6.0 m/s. If the coefficient of kinetic friction between ice and puck is 0.050, how far will the puck slide before stopping?
37 m
A 1 200-kg automobile moving at 25 m/s has the brakes applied with a deceleration of 8.0 m/s2. How far does the car travel before it stops?
39 m
A rock is rolled in the sand. It starts at 5.0 m/s, moves in a straight line for a distance of 3.0 m, and then stops. What is the magnitude of the average acceleration?
4.2 m/s2
A 20-N crate starting at rest slides down a rough 5.0-m long ramp, inclined at 25° with the horizontal. 20 J of energy is lost to friction. What will be the speed of the crate at the bottom of the incline?
4.7 m/s
A baseball batter hits an incoming 40-m/s fastball. The ball leaves the bat at 50 m/s after a ball on bat contact time of 0.030 s. What is the force exerted on the 0.15-kg baseball?
450 N
A cart starting from rest rolls down a hill and at the bottom has a speed of 4 m/s. If the cart were given an initial push, so its initial speed at the top of the hill was 3 m/s, what would be its speed at the bottom?
5 m/s
An object weighs 100 N. If the gravitational constant g were half of what it is currently, what would the weight of the object be?
50 N
A 60 kg woman runs up a flight of stairs having a rise of 4.0 m in a time of 4.2 s. What average power did she supply?
560 W
A barefoot field goal kicker imparts a speed of 30 m/s to a football at rest. If the football has a mass of 0.50 kg and time of contact with the football is 0.025 s, what is the force exerted on the foot?
600 N
A golf ball hits a wall and bounces back at 3/4 the original speed. What part of the original kinetic energy of the ball did it lose in the collision?
7/16
What is the minimum amount of energy required for an 80 kg climber carrying a 20 kg pack to climb Mt. Everest, 8 850 m high?
8.67 MJ
An automobile of mass 2 000 kg moving at 30 m/s is braked suddenly with a constant braking force of 10 000 N. How far does the car travel before stopping?
90 m
A sled weighs 100 N. It is held in place on a frictionless 20° slope by a rope attached to a stake at the top; the rope is parallel to the slope. What is the normal force of the slope acting on the sled?
94 N
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
Paul and Kathleen start from rest at the same time on frictionless water slides with different shapes. Who makes it to the bottom first?
Kathleen
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
You kick a smooth flat stone out on a frozen pond. The stone slides, slows down and eventually stops. You conclude that:
a net force acted on it all along
A horizontal force of 750 N is needed to overcome the force of static friction between a level floor and a 250-kg crate. What is the acceleration of the crate if the 750-N force is maintained after the crate begins to move and the coefficient of kinetic friction is 0.12?
a. 1.8 m/s2 b. 2.5 m/s2 c. 3.0 m/s2 d. 3.8 m/s2
Paul and Kathleen start from rest at the same time on frictionless water slides with different shapes. At the bottom, whose velocity is greater?
both the same
In a baseball game, the catcher stops a 90-mph pitch. What can you say about the work done by the catcher on the ball?
catcher has done negative work
A box sits on a flat board. You lift one end of the board, making an angle with the floor. As you increase the angle, the box will eventually begin to slide down. Why?
component of the gravity force parallel to the plane increased and normal force exerted by the board decreased.
Consider a cart on a horizontal frictionless table. Once the cart has been given a push and released, what will happen to the cart?
continue with constant velocity
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
By what factor does the kinetic energy of a car change when its speed is tripled?
factor of 9
A truck, initially at rest, rolls down a frictionless hill and attains a speed of 20 m/s at the bottom. To achieve a speed of 40 m/s at the bottom, how many times higher must the hill be?
four times the height
Which of the following is an example of a nonconservative force?
friction
You throw a ball straight up into the air. In addition to gravity, the ball feels a force due to air resistance. Compared to the time it takes the ball to go up, the time it takes to come back down is:
greater
The unit of power, watt, is dimensionally the same as:
joule/second
The SI units for k, the spring constant, are equivalent to:
kg / s^2
Which of the following is that form of energy associated with an object's motion?
kinetic
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
Is it possible to do work on an object that remains at rest?
no
You put your book on the bus seat next to you. When the bus stops suddenly, the book slides forward off the seat. Why?
no net force acted on it
A box sits in a pickup truck on a frictionless truck bed. When the truck accelerates forward, the box slides off the back of the truck because:
no net force acted on the box
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
We just decided that the cart continues with constant velocity. What would have to be done in order to have the cart continue with constant acceleration?
push the cart continuously
You and your friend both solve a problem involving a skier going down a slope, starting from rest. The two of you have chosen different levels for y = 0 in this problem. Which of the following quantities will you and your friend agree on?
skier's change in PE and skier's final KE
A mass m is placed on an inclined plane (m > 0) and slides down the plane with constant speed. If a similar block (same m) of mass 2m were placed on the same incline, it would:
slide down at constant speed
In the previous question, just before hitting the ground, what is the final speed of the heavy stone compared to the light one?
the same
Two paths lead to the top of a big hill. One is steep and direct, while the other is twice as long but less steep. How much more potential energy would you gain if you take the longer path?
the same
A book is lying at rest on a table. The book will remain there at rest because:
there is no net force on the book
A box is being pulled up a rough incline by a rope connected to a pulley. How many forces are doing work on the box?
three forces
A box sliding on a frictionless flat surface runs into a fixed spring, which compresses a distance x to stop the box. If the initial speed of the box were doubled, how much would the spring compress in this case?
twice as much
Two stones, one twice the mass of the other, are dropped from a cliff. Just before hitting the ground, what is the kinetic energy of the heavy stone compared to the light one?
twice as much
The quantity of work equal to one joule is also equivalent to which of the following?
watt - s
In the terminology a 500-N block, the 500-N refers to the block's:
weight
Is it possible for the gravitational potential energy of an object to be negative?
yes
A hockey puck slides on ice at constant velocity. What is the net force acting on the puck?
zero
A very light cart holding a 300-N box is moved at constant velocity across a 15-m level surface. What is the net work done in the process?
zero
As a car moves forward on a level road at constant velocity, the net force acting on the tires is:
zero
You lift a book with your hand in such a way that it moves up at constant speed. While it is moving, what is the total work done on the book?
zero
