Physics Midterm Questions

During batting practice, a 0.30 kg baseball is hit with a bat that exerts a force of 350 N on the ball. The ball left the bat at 80.0 m/s. If the incoming pitch was traveling at 60.0 m/s, how long did the ball stay in contact with the bat?

0.12 s

A 1.00•10^3 kilogram car is driven clockwise around a flat circular track of radius 25.0 meters. The speed of the car is a constant 5.00 meters per second. What minimum friction force must exist between the tires and the road to prevent the car from skidding as it rounds the curve?

1.00•10^3 N

A skateboarder with a mass of 50.0 kg is riding on a half-pipe as shown in the diagram above. He has a speed of 5.00 m/s at the bottom. What vertical distance will the skateboarder climb to assuming no energy is lost to friction?

1.28 m

What is the force of gravitational attraction between 2 dust particles that each have a mass of 0.0033 kg that are separated from each other by a distance of 2.0 m?

1.8•10-16 N

A displacement vector is 34.0 m in length and is directed 60.0° west of north. What are the components of this vector?

17.0 m Northward, 29.4 m Westward

The weight lifter used a force of 980 N to raise a barbell over his head in 5.21 seconds. Approximately how much work did he do in raising the barbell?

2,000 J

A 0.40 kg flashlight is constructed to withstand a specific force of impact that protects the bulb. A standard 0.10 second is used as the time-of-impact in calculating a flashlight's specifications. What is the impact force on the 0.40 kg flashlight if it falls 2.5 meters and hits a concrete floor at 7.0 m/s, stopping in 0.10 seconds?

28 N (mass*velocity=force*time)

A 1,000 kg cannon fires a 10 kg projectile horizontally at a velocity of 300 m/s. What is the magnitude of the recoil velocity of the cannon?

3 m/s

Neglecting air resistance, if a ball is thrown at 4.5 m/s horizontally from a 94 m high cliff, how far has the ball fallen after 2.7 s?

36 m

Mithra is an unknown planet that has two moons, A and B, in circular orbits around it. The table summarizes the hypothetical data about these moons. What is the magnitude of the maximum gravitational force that Moon A exerts on Moon B?

4.0•10^14 N

A skydiver whose mass is 60.0 kg is accelerating downward toward the Earth at 2.50 m/s2. What is the magnitude of the air resistance force acting upward on the skydiver?

438 N

Centripetal force Fc acts on a car going around a curve. If the speed of the car were twice as great, the magnitude of the centripetal force necessary to keep the car moving in the same path would be?

4Fc

You walk 53.0 m to the north, then you turn 60.0° to your right and walk another 45.0 m. Determine the approximate direction of your displacement vector. Express your answer as an angle relative to east.

69° N of E

A jet plane flying 600.0 m/s experiences an acceleration of 4.0 g's when pulling out of a circular dive. What is the radius of curvature of the circular part of the path in which the plane is flying?

9200 m

A simple machine often multiplies your:

Force

A rock is thrown from the upper edge of a tall cliff at some angle above the horizontal. It reaches its highest point and starts falling down. Which of the following statements about the rock's motion are true just before it hits the ground?

Its horizontal velocity component is the same as it was just as it was launched.

Two friends stand on rollerskates, facing each other within arm's reach. Jim pushes gently on his friend Tony's upraised palms. What happens?

Jim and Tony roll in opposite directions.

Which of the following equipment is the best choice for investigating elastic or nearly elastic collisions?

Marble launcher that causes two marbles to collide with eachother

Two cars having different weights are traveling on a level surface at different constant velocities. Within the same time interval, greater force will always be required to stop the car that has the greater

Momentum

Brett lifts a 300 N crate from the ground to a loading dock 1 meter high. Teresa pushes the same crate to the loading dock up a ramp 3 meters long. Compare the amount of work being done by Brett and Teresa if this was a real situation.

Teresa does more work, because sliding friction is greater than air friction

Which of the following statements are true about an object in two-dimensional projectile motion with no air resistance?

The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward.

A coin is flipped straight up from the surface of the Earth. Which one of the following statements describes the energy transformation of the coin as it rises? Neglect air resistance.

The kinetic energy decreases and the potential energy increases

Which of the following is equal to an object's acceleration?

The slope of that object's velocity-time graph

An object is launched across a room. How can a student determine the average horizontal velocity of the object using a meter stick and a calculator?

The student can measure the horizontal travel distance, compute the flight time from the vertical drop, and then calculate the average horizontal velocity.

One sphere of mass 2.0 kg is moving at 5.0 m/s to the right until it collides with a stationary, 1.0 kg sphere. After the collision, both spheres travel to the right: the 2.0 kg sphere at 1.0 m/s, and the 1.0 kg sphere at 2.0 m/s. What kind of collision took place?

This is an inelastic (but not perfectly inelastic) collision.

Jim (80.0 kg) and Tony (100.0 kg) stand motionless on ice skates, facing each other at arm's length on a smooth, frozen pond. Which of the following actions will give Tony the greatest speed?

Tony pushes Jim with 200.0 N of force for 0.080 s.

Which of the following is equal to the area under an acceleration-time graph?

Velocity

Suppose you are in a car that is going around a curve. The speedometer reads a constant 30 kilometers per hour. Which of the following is NOT true?

Your velocity is constant

Suppose an object is freely falling downwards. In the absence of air resistance, each second the object falls

a larger distance than in the second before

Which object has the greatest inertia?

a seated high school student

James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. If there is no air resistance, when they reach the lake below

the splashdown speed of John is larger than that of James.

A 20 kg shopping cart moving at a velocity of 0.5 m/s collides into a store wall and stops. The momentum of the shopping cart

decreased

The formula for work is:

force • change in displacement

The gravitational field of the planet Earth

has a strength of 9.80 newtons per kilogram

In the speed vs. time graph above, the object at point C:

has negative acceleration

For general projectile motion with no air resistance, the horizontal component of a projectile's acceleration

is always zero

A projectile is fired horizontally in a vacuum. The projectile maintains its horizontal component of speed because it

is not acted on by any horizontal forces

A father (100 kg) and his son (50 kg) are jogging at the same speed. Which statement is true about the kinetic energies (K) of the father and the son?

kinetic energy of the father = double the kinetic energy of the son

The diagram above represents two masses before and after they collide. Before the collision, mass mA is moving to the right with speed v, and mass mB is at rest. Upon collision, the two masses stick together. Which expression represents the speed, v', of the masses after the collision? [Assume no outside forces are acting on mA or mB.]

mAv / (mA + mB)

The formula for momentum is

mass • velocity

You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the friction between the tires and the road to become zero. While the car is on the ice, it

moves along a straight-line path in its original direction.

A player kicks a soccer ball in a high arc toward the opponent's goal. At the highest point in its trajectory

neither the ball's velocity nor its acceleration are zero.

A large moving ball collides with a small stationary ball. The momentum

of the large ball decreases, and the momentum of the small ball increases

If the earth were four times as far from the sun as it is now, the gravitational force between it and the sun would be

one-sixteenth as strong

When you stretch a rubber band and then shoot it, the ________ from when it stretched changes to kinetic energy.

potential energy

The graph above represents the motion of an object. According to the graph, as time increases, the velocity of the object

remains the same

The measure of "stretch" in an ellipse is

the eccentricity

Consider a package which is sliding down a loading ramp at constant speed. In this case

the net force on the package is zero which is why it is not accelerating

A spring-loaded ballistic cart measuring 190 g is in contact with a second 530 g cart. The carts are initially at rest on a level surface. The spring is released and the lighter cart is observed to move at +0.69 m/s afterward. What is the velocity of the other cart?

-0.25 m/s

A car is moving with a speed of 65.0 km/hr when a squirrel runs into the road in front of your car. The driver then hits the brakes and reduces the speed of the car to 25.0 km/hr over a time period of 2.00 seconds. What is the average rate at which the speed of the car decreases during this time period?

-20.0 km/hr/s

When Earth and the Moon are separated by a distance of 3.84•108 meters, the magnitude of the gravitational force of attraction between them is 2.0•1020 Newtons. What would be the magnitude of this gravitational force of attraction if Earth and the Moon were separated by a distance of 1.92•108 meters?

...

A train car with a mass of 3.00•104 kg traveling north at 1.5 m/s collides and couples with a 3.20•104 kg train car going south at 0.80 m/s. What is the velocity of the coupled cars after the collision?

0.31 m/s north

A ball is hit with a bat. A student determines that the momentum of the ball is 1.0 kilogram meter per second. What is the mass of the ball if it has a velocity of 2.0 meters per second?

0.50 kg

A 3.00 kilogram mass is attached to a spring (k = 30.0 N/m) . The mass is pulled 0.200 meters from the spring's equilibrium position. How much spring potential energy is being stored by the mass-spring system?

0.600 J

If car I in the data table above were to collide head-on with car IV and the two cars locked together into a single moving pile, what would their combined momentum be?

1.0 kgm/s west

The graph represents the position of a cart as a function of time. What is the velocity at 6 seconds?

1.0 m/s

A 7.0 kg block sliding on a frictionless surface is moving with an initial velocity of 8.0 m/s. An impulse is applied to the block as shown on the graph. What is the block's speed at time t = 6 s?

10.3 m/s

A motorboat is driven across a river at 3.00 km/hr at right angles to a current that is flowing at 10.0 km/hr. What is the resulting speed of the motorboat?

10.4 km/hr

The diagram above shows points A, B, and C at or near the Earth's surface. As a mass is moved from A to B, 100 joules of work are done against gravity. What is the amount of work done against gravity as an identical mass is moved from A to C?

100 J

A block sliding on a frictionless surface is moving with a velocity of 9.0 m/s. The mass of the block is 8.0 kg. An impulse is applied on the block as shown on the graph. What is the block's speed at time t = 6 s?

11 m/s

The reading on the spring scale is approzimately

110 N

An airplane with an airspeed of 120.0 km/hr has a heading of 30.0 degrees east of north in a wind that is blowing toward the west at 30.0 km/hr. What is the approximate speed of the plane relative to the ground?

110 km/hr

When a 12 Newton horizontal force is applied to a box on a tabletop, the box remains at rest. The force of static friction acting on the box is

12 N

A 60.0 kilogram car travels clockwise in a horizontal circle of radius 10.0 meters at 5.0 meters per second. The magnitude of the centripetal force acting on the car is

150 N

A car starts from rest and uniformly accelerates to a final speed of 20.0 meters/second in a time of 15.0 seconds. How far does the car travel during this time?

150. m

A satellite is moving in space with a linear velocity of 230.0 m/s. The mass of the satellite is 290 kg. The satellite fires its rockets, creating the impulses shown on the graph. The forces are applied along the direction of motion. What is the satellite's velocity at time t = 7.0 s?

175 m/s

A student eats a candy bar that contains 1,570,000 J of energy. If the student has a mass of 81.8 kg, how high will he have to climb a ladder to completely burn off the energy gained by eating the candy bar?

1960 m

A rowboat has a momentum of 240 kgm/s. If the rowboat has a mass of 115 kg, what is its speed?

2.1 m/s

A bird flies 2.0 km to the south, then 0.2 km to the north. What is the distance flown by the bird?

2.2 km

You are the science officer on a visit to a distant solar system. Prior to landing on a planet you measure its diameter to be 1.8•107 m. You have previously determined that the planet orbits 2.9•1011 m from its star with a period of 402 earth days. Once on the surface you find that the acceleration due to gravity is 19.5 m/s2. What are the masses of the planet and the star respectively?

2.4•10^25 kg, 1.2•10^31 kg

A 75 kg object traveling 15 m/s collides with and sticks to a 315 kg object initially at rest. What is the final velocity of the two objects?

2.88 m/s

A 0.05 kg bullet is fired from a 4.0 kg rifle that is initially at rest. If the bullet leaves the rifle with a momentum having a magnitude of 20 kgm/s, the rifle will recoil with a momentum of having a magnitude of

20 kgm/s

A hockey puck slides off the edge of a platform with an initial velocity of 20.0 m/s horizontally. The height of the platform above the ground is 2.0 m. What is the approximate magnitude of the velocity of the puck just before it touches the ground? You can neglect air resistance.

20 m/s

The graph shows the acceleration of a car over time. If the car starts from rest, what is the velocity of the car after 5 seconds?

20 m/s

A car traveling on a straight road at 15.0 m/s accelerates uniformly to a speed of 21.0 meters per second in 12.0 seconds. The total distance traveled by the car in this 12.0 second time interval is

216 meters

If an automobile travels at 30 m/s for 2 minutes, the car has traveled:

3,600 meters

A 60.0 kg student on ice skates stands at rest on a frictionless frozen pond holding a 10.0 kg brick. He throws the brick east with a momentum of 180.0 kgm/s. What is the resulting velocity of the student?

3.00 m/s west

A toy cart with a mass of 1.20 kg moves at a speed of 2.40 m/s. How much mechanical kinetic energy does it have?

3.46 J

If the average speed of a drag racing car is 0.069 kilometers per second, how long would it take the car to complete a 1/4 km (0.25 km) straight track?

3.6 s

A mass of m1 = 0.5 kg is sitting on a horizontal surface which has a coefficient of sliding friction of mk = 0.8. How much force needs to be applied to this mass so as to pull the mass at a constant speed?

3.9 newtons

A ball rolls over the edge of a platform with only a horizontal velocity. The height of the platform is 1.6 m and the horizontal range of the ball from the base of the platform is 20.0 m. What is the horizontal velocity of the ball just before it touches the ground? Neglect air resistance.

35 m/s

The weight lifter used a force of 980 N to raise the barbell over his head in 5.21 seconds. Approximately how much power did the weight lifter generate in raising the barbell?

384 W

An airplane flies between two points on the ground that are 500 km apart. The destination is directly north of the point of origin of the flight. The plane flies with an airspeed of 120 m/s. If a constant wind blows at 10 m/s toward the west during the flight, what direction must the plane fly relative to the air to arrive at the destination?

4.8° east of north

The diagram above shows the velocities of two cyclists. From the frame of reference of cyclist 2, what is the speed of cyclist 1?

5 m/s west

A 6.0 kg ball of clay travelling at 10.0 m/s collides with a 10.0 kg ball of clay travelling in the same direction at 2.0 m/s. What is their combined speed if the two balls stick together when they touch?

5.0 m/s

A 5.23 meter ladder leans against a wall (at a 29.4 degree angle of elevation). What is the height above the ground where the top of the ladder makes contact with the wall?

5.23 meters x sin (29.4°)

A model rocket with an initial mass of 3.0 kg is launched horizontally by burning and expelling 760 g of fuel with a velocity of 150 m/s. What is the velocity of the rocket after the fuel is expelled?

51 m/s

A 0.149 kg baseball, initially moving at 15 m/s is brought to rest in 0.04 seconds by a baseball glove on a catcher's hand. The magnitude of the average force exerted on the ball by the glove is

56 N

You are standing on a bathroom scale (which happens to read in Newtons) in an elevator. While at rest the scale you weigh 491 Newtons. How much would the bathroom scale read when the elevator is accelerating upwards at 1.5 m/s^2?

566 N

The acceleration due to gravity on the Moon is only one-sixth of that on Earth, and the Moon has no atmosphere. If you hit a baseball on the Moon with the same effort (and therefore at the speed and angle) as on Earth, how far would the ball would travel on the Moon compared to on Earth? Neglect air resistance on Earth.

6 times as far as on Earth

A crane lifts a load of steel 250.0 meters into the air. The steel has a mass of 2,500.0 kg. How much work did the crane do on the steel?

6,130,000 J

What is the momentum of a cat of mass 4.0 kg that is running south with a speed of 1.5 m/s?

6.0 kgm/s south

A hockey puck slides off the edge of a horizontal platform with an initial velocity of 20.0 m/s horizontally and experiences no significant air resistance. The height of the platform above the ground is 2.0 m. What is the magnitude of the vertical component of the velocity of the puck just before it hits the ground?

6.3 m/s

A 13 N horizontal force acts in the same direction as a 6.4 kg block as it slides 2.5 m/s on a frictionless, horizontal surface for 2.1 s. What is the speed of the block after force is applied?

6.8 s

What is the momentum of a dog of mass 20 kg that is running east with a speed of 3 m/s?

60 kgm/s east

How much time does a car with an acceleration of 5.00 m/s² take to go from 5.00 m/s to 40.0 m/s?

7.00 s

A crane lifts a load of steel 250.0 meters into the air. The steel has a mass of 2,500.0 kg. If the crane performed this feat in 85 seconds, how much power does the crane use?

72,000 W

A cannon with a barrel velocity of 140 m/s launches a cannonball horizontally from a tower. Neglecting air resistance, what vertical distance will the cannonball have fallen after 4.00 seconds?

78.5 m

During the first 10 seconds of a rocket launch, the momentum of the rocket increased by 8000 kgm/s. What was the impulse applied to the rocket during this time?

8,000 Ns

An object travels around a 120 m radius circular path at a constant 70.0 m/s. The centripetal force on the object is 35,000 N. What is the mass of the object?

860 kg

A golf ball is hit at an angle of 45o above the horizontal. What is the acceleration of the golf ball at the highest point in its trajectory? [ignore air resistance]

9.80 m/s² downwards

A stone is thrown horizontally with an initial speed of 10.0 m/s from the edge of a cliff. A stopwatch measures the stone's trajectory time from the top of the cliff to the bottom to be 4.30 s. What is the approximate height of the cliff if air resistance is negligibly small?

91 m

A wooden block is at rest on a horizontal steel surface. If a 10. newton force applied parallel to the surface is required to overcome static friction and set the block in motion, how much force is required to keep the block moving at constant velocity?

< 10 N

A wound spring provides the energy to propel a toy car across a level floor. At time ti, the car is moving at speed vi across the floor and the spring is unwinding, as shown below. At time tf, the spring has fully unwound and the car has coasted to a stop.

Both elastic potential energy and kinetic energy at ti are converted to thermal energy at tf

Mary and Debra stand on a snow-covered roof. They both throw snowballs with the same initial speed, but in different directions. Mary throws her snowball downward, at 30° below the horizontal; Debra throws her snowball upward, at 30° above the horizontal. Which of the following statements are true about just as the snowballs reach the ground below?

Both snowballs will hit the ground woth the same speed

You eat a large meal and then hike up a hill. What kind of energy transformation(s) is your body performing?

Chemical energy to kinetic energy and gravitational potential energy

The diagram above represents the relationship between velocity and time of travel for four cars, A, B, C, and D, in straight-line motion. Which car has the greatest acceleration during the time interval 10.0 seconds to 15.0 seconds?

D

Which of the following energy sources is renewable?

Hydroelectric

A small insect collides and sticks to the windshield of a large car in a head on collision. The magnitudes of the I. Average force of the impact on the car and the impact are the same II. Impulses on the car and the insect are the same III. Changes in speed of the car and insect are the same IV. Changes in momentum of the car and the insect are the same

I, II, and IV only

Which car in the data table above has the greatest momentum?

III

Objects tend to resist changes in motion. This property is called:

Inertia

A 1300 kg car with 370 kg of passengers and cargo is moving at 72 m/s. Suddenly, the driver applies the brakes and the car skids to a stop. What happens to the momentum that the car (and its contents) had before braking?

It is transferred to the pavement (and the Earth).

In an inelastic collision, what quantities are conserved?

Momentum only

A ball is released from the top of an inclined plane as shown below. Ignoring friction, where will the gravitational potential energy (U) and kinetic energy (K) of the ball be at a maximum?

Potential energy at J, Kinetic energy at M

What does the slope of the graph above represent? (Work vs. Time)

Power

Based on the setup below, which of the following statements is true? (Assume the car starts at rest and there is no friction.)

The car will never reach the egg

A steel ball traveling at 6 m/s hits a stationary line of three steel balls of the same mass as the original. Which statement is true if the collision is perfectly elastic?

The original ball stops and a single ball moves to the right at 6 m/s.

Let the orbital radius of a planet be R and let the orbital period of the planet be T. What quantity is constant for all planets orbiting the sun, assuming circular orbits?

T²/R³

The graph above represents the relationship between gravitational force and mass for objects near the surface of Earth. The slope of the graph represents the

acceleration due to gravity

One possible unit of speed is

all of these listed are correct

A spaceship drifts sideways in outer space from point P to point Q as shown above. The spaceship is subject to no outside forces. Starting at position Q, the spaceship's engine is turned on and produces a constant thrust (force on the spaceship) at right angles to the line PQ. The constant thrust is maintained until the spaceship reaches a point R in space. As the spaceship moves from point Q to point R its speed is

continuously increasing