Physics Final Compiled HW questions

If an object moves with constant acceleration, its velocity must

change by the same amount each second

It is correct to say that impulse is equal to

change in momentum

In how many of the following situations does the car have a westward acceleration? -- The car travels westward at constant speed. -- The car travels eastward and speeds up. -- The car travels westward and slows down. -- The car travels eastward and slows down. -- The car starts from rest and moves toward the east.

#1

One force vector has (x, y) components (5 N, 3 N) and a second has (x, y) components (2 N, 2 N). Both forces act on the same object. These forces produce a net force with components _____ and magnitude _____ .

(7N , 5N) , 8.6 N

A block slides on a track from A to B to C to D. The section from A to B to C is frictionless, but for the section from C to D the coefficient of friction is not zero.Is the block's mechanical (ordered) energy increasing, decreasing, or constant in (a) region AB, (b) region BC, and (c) region CD?

(A) CONSTANT (B) CONSTANT (C) DECREASING

(A) Can two force vectors of unequal magnitude sum to zero net force? (B) Can three force vectors of equal magnitude sum to zero net force?

(A) no (B) yes

Two identical carts labeled A and B are initially resting on an air track. The coordinate system for describing the system is shown. The cart on the right, cart B is given a push to the left and is released. The clock is then started. At t = 0, cart B moves in the direction shown with a speed v0. They hit and stick to each other. The graphs below describe some of the variables associated with the motion as a function of time. For the experiment described and for each item in the list below, identify which graph is a possible display of that variable as a function of time assuming a proper scale. "The system" refers to carts A and B together. (i) the momentum of cart A (ii) the momentum of cart B (iii) the total momentum of the system (iv) the total kinetic energy of the system

(i) #1 (ii) #3 (iii) #6 (iv) #2

A ball is launched up a ramp by a spring as shown in the figure. At the time when the clock starts, the ball is near the bottom of the ramp and rolling up the ramp as shown. It goes to the top and then rolls back down.For the graphs shown below, the horizontal axis represents the time. The vertical axis is unspecified. Select the number of the graph that could correctly represent (i) the x-component of the ball's position, (ii) the x-component of the ball's velocity, (iii) the x-component of the ball's acceleration.

(i) 8 (ii) 3 (iii) 2

An object's motion is restricted to one dimension along the positive x-axis. It stays to the right of the origin. Answer each of the questions below by selecting the velocity versus time graph that is the best choice to describe the answer. (i) Which velocity graph shows an object moving away from the origin with constant velocity? (ii) Which velocity graph shows an object at rest? (iii) Which velocity graph shows an object moving toward the origin with constant velocity? (iv) Which velocity graph shows an object changing direction?

(i) C , (ii) G , (iii) D and (IV) F

A bicyclist rides for 25 s along a straight line that corresponds to the x-axis covering a distance of 450 m. She then turns her bike around; that takes another 20 s. Finally, she rides back to where she started (450 m in the -x-direction) for 30 s. What is the magnitude of her average velocity for this trip?

0 m/s

An ornament of mass 40.0 g is attached to a vertical ideal spring with a force constant (spring constant) of 20.0 N/m. The ornament is then lowered very slowly until the spring stops stretching. How much does the spring stretch?

0.0196

A 50.0-kg crate is being pulled along a horizontal smooth surface. The pulling force is 10.0 N and is directed 20.0° above the horizontal. What is the magnitude of the acceleration of the crate?

0.188 meter per square seconds

Uniform Circular Motion: A 20-g bead is attached to a light 120-cm-long string as shown in the figure. This bead moves in a horizontal circle with a constant speed of 1.5 m/s. What is the tension in the string if the angle α is measured to be 25°?

0.22 N

An object slides on a level floor. It slows and comes to a stop with a constant acceleration of magnitude 2.4 m/s2. What is the coefficient of kinetic friction between the object and the floor?

0.24

A cat leaps to try to catch a bird. If the cat's jump was at 60° off the ground and its initial velocity was 2.74 m/s, what is the highest point of its trajectory, neglecting air resistance?

0.29 m

Another scheme to catch the roadrunner has failed and a safe falls from rest from the top of a 30.0 m high cliff toward Wile E. Coyote, who is standing at the base. Wile first notices the safe after it has fallen 15 m. How long does he have to get out of the way?

0.72 s

Planet W-70 has a radius of 2.48 × 107 m and an escape velocity of 23,300 m/s. What is the mass of W-70? (G = 6.67 × 10-11 N ∙ m2/kg2)

1.01 x 10^26 kg

At their closest approach, Venus and Earth are 4.20 × 1010 m apart. The mass of Venus is 4.87 × 1024 kg, the mass of Earth is 5.97 × 1024 kg, and G = 6.67 × 10-11 N ∙ m2/kg2. What is the magnitude of the gravitational force exerted by Venus on Earth at that point?

1.10 x 10^18 N

A 12-L volume of oil is subjected to pressure which produces a volume strain of -3.0 × 10-4. The bulk modulus of the oil is 6.0 × 109 Pa and is independent of the pressure. The change in the pressure of the oil in megapascals is closest to

1.8 MPa

A motor is used to lift an object weighing 15 N a distance of 2 m in 3 seconds. Assuming no conversion of ordered into thermal energy, what is the power output of the motor?

10 W

A ball is thrown with an initial velocity of 20 m/s at an angle of 60° above the horizontal. If we can neglect air resistance, what is the horizontal component of its instantaneous velocity at the exact top of its trajectory?

10 m/s

You are traveling at 55 mi/h along the +x-axis relative to a straight, level road and pass a car that is traveling at 45 mi/h. The relative velocity of your car to the other car is

10 mi/h

As a bacterium swims through water it propels itself with its flagella so as to overcome the frictional drag forces and move at, more or less, constant velocity of 100 micrometer/s for periods of time. If the frictional drag force on a bacterium is 0.1 N, how much work does the bacterium do in 1 s?

10 microjoule

Uniform Circular Motion: A 2.0-kg ball is moving with a constant speed of 5.0 m/s in a horizontal circle whose diameter is 1.0 m. What is the magnitude of the net force on the ball?

100 N

Use g = 10 m/s2. An airplane is flying horizontally over level ground. It has an altitude of 500 m and a velocity of 100 m/s. As the airplane passes directly above a cross marked on the ground, an object is released. How far away from the cross will the object land?

1000 m

A person walks from A to B along a circular path of radius 5.00 m around 1/2 of the circle. What is the magnitude (in m) of the displacement vector?

10m

A steel wire, 3.2 m long, has a diameter of 1.2 mm. The wire stretches 1.6 mm when it bears a load. Young's modulus for steel is 2.0 × 1011 Pa. The mass of the load is closest to

12 kg

Assume g = 10 m/s2. A football's mass is 0.45 kg. If you did the 60 J of work on the football, while throwing it straight up, how high would it go?

13.3 m

A 60 kg runner with a speed of 5.1 m/s makes a sharp turn with a radius of 1.2 m to avoid a collision. What is the magnitude of the frictional force (in N) the ground exerts on the runner during the turn?

1301

Satellite Motion: Find the orbital speed of an ice cube in the rings of Saturn. The mass of Saturn is 5.68 × 1026 kg, and use an orbital radius of 1.00 × 105 km. (G = 6.67 × 10-11 N ∙ m2/kg2)

19.5 km

A 3.0-kg mass and a 5.0-kg mass hang vertically at the opposite ends of a very light rope that goes over an ideal pulley. If the masses are gently released, what is the resulting acceleration of the masses?

2.5 m/s2

A football kicker is attempting a field goal from 44 m out. The ball is kicked and just clears the lower bar with a time of flight of 2.9 s. If the angle of the kick was 45°, what was the initial speed of the ball, assuming no air resistance?

21.5 m/s

You are sanding a table, sliding the sandpaper back and forth across the table for 20 minutes. During that time you exert a force of 25 N on the paper and move it 1000 m. How much work have you done?

25000 J

A 750 kg automobile is traveling horizontally with speed 20.0 m/s. What is the automobile's new speed after an additional 150000 J of net work has been done on the car?

28.3 m/s

A constant horizontal force is exerted on a cart that is initially at rest on a frictionless horizontal track. The force acts for a time t during which the cart moves a distance d. If the force is halved and applied to the same cart for twice the time, the cart will move a distance

2d

A 6.0-kg box slides down an inclined plane that makes an angle of 39° with the horizontal. If the coefficient of kinetic friction is 0.40, at what rate does the box accelerate down the slope?

3.1 m/s2

A girl pulling a sled exerts a 20 N force horizontally for 40 s. How much power does she generate while moving the sled 60 m?

30 W

You walk in a given direction for 15 m during the first 4 seconds of a trip and then 25 m during the next 6 seconds. Your average speed is equal to

4 m/s

A 15-kg block is on a frictionless ramp that is inclined at 20° above the horizontal. It is connected by a very light string over an ideal pulley at the top edge of the ramp to a hanging 19-kg block, as shown in the figure. The string pulls on the 15-kg block parallel to the surface of the ramp. Find the magnitude of the acceleration of the 19-kg block after the system is gently released?

4.0 m/s2

A person walks first at a constant speed of 6 m/s along a straight line from point A to point B and then back along the line from B to A at a constant speed of 4 m/s. What is her average speed over the entire trip? Hint: Assume the distance between A and B is d. How much distance does the person cover on her trip? How long does it take her to cover this distance?

4.8 m/s

You operate a 120 W light bulb for 1 hour. How much energy did you use? (1 W = 1 J/s)

432000

A 2 kg mass is at x = 0 m, y = 2 m, and a 3 kg mass is at x = 2 m, y = 0 m. The x- and y-coordinates, respectively, of the center of mass of this system are

6/5 m , 4/5 m

The magnitude of the force vector with (x, y) components (5 N, 5 N) is

7.1 N

A jet plane flying 600 m/s experiences an acceleration of 4.0 g when pulling out of the circular section of a dive. What is the radius of curvature of this section of the dive?

9.2 km

Uniform Circular Motion: A jet plane flying 600 m/s experiences an acceleration of 4.0 g when pulling out of the circular section of a dive. What is the radius of curvature of this section of the dive?

9.2 km

A ball is fired by a cannon from the top of a cliff as shown in the figure below. Which of the path would the cannonball most closely follow?

B;

Two pitchers are standing side by side, and simultaneously throw baseballs A and B. The balls follow the parabolic trajectories shown. Which of the following statements is true?

Ball B hits the ground before ball A

Bob and Carl are riding on a merry-go-round. Bob is closer to the center of the merry-go-round. Who has the greater centripetal acceleration?

Bob

You need to loosen a very tight bolt. You have one wrench and you exert maximum force. Which configuration shown below gives you maximum chance of success?

C

Car 1 starts from rest along a straight highway with constant acceleration a = 1 m/s2. Car 2 passes car 1 with constant velocity of 120 km/hr. Which car is acted on by a larger net force?

Car 1

A small metal cylinder rests on a circular turntable, rotating at a constant speed, as illustrated in the diagram above. Which of the sets of vectors best describes the velocity, acceleration, and net force acting on the cylinder at the position indicated in the diagram?

D

Gravitational Force: Two small objects, with masses m and M, are originally a distance r apart, and the magnitude of the gravitational force on each one is F. The masses are changed to 2m and 2M, and the distance is changed to 4r. What is the magnitude of the new gravitational force?

F/4

Two small objects, with masses m and M, are originally a distance r apart, and the magnitude of the gravitational force on each one is F. The masses are changed to 2m and 2M, and the distance is changed to 4r. What is the magnitude of the new gravitational force?

F/4

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal. What must be true about normal force F on the block due to the ramp?

F=mg cos (theta)

Consider the following five graphs (note the axes carefully). Which of these represent(s) one-dimensional motion at constant acceleration, including a = 0?

I, II, IV and V only.

Look at the position versus time graph below. Do A and B ever have the same speed?

No, A and B never have the same speed

Consider a rod of uniform density with an axis of rotation through its center and an identical rod with the axis of rotation through one end. Which has the larger moment of inertia about its axis of rotation?

Rod B with the axis through one hand

Which statement best describes Earth's rotation about its axis?

The angular acceleration is zero at all points on Earth's surface.

An object moves in a circle with constant speed.

The object is accelerating. It is acted on by a radial force, pointing towards the center of the circle.

During a July 4th firecracker party, a pop bottle rocket lying still on the ground explodes, sending fragments everywhere. If the momentum of the pop bottle rocket (ignore friction!) initially at rest is conserved during an explosion, what can be said about the kinetic energy of various fragments after the collision?

The total kinetic energy afterwards is greater than what it was initially.

You throw a ball straight up. Compare the sign of the work done by the force of gravity while the ball goes up with the sign of the work done by gravity while it goes down.

The work done by the force of gravity is negative on the way up and positive on the way down.

Suppose you are on a cart, initially at rest on a frictionless, horizontal track. You throw a series of identical balls against a wall that is rigidly mounted to the cart. If the balls are thrown at a steady rate and bounce straight back, is the cart put into motion?

Yes, it starts to move to the left and steadily gains speed.

Can an object's velocity change direction when its acceleration is constant?

Yes, this is possible, and a rock thrown straight up is an example.

The graph in the figure shows the tensile stress as a function of the tensile strain in a certain wire. What does the slope of this graph give us for this wire?

Young's modulus for the material of the wire

Work, as defined in physics is

a scalar quantity, a positive or negative number with units

A woman weighing 500 N stands in an elevator that is traveling upward. At a given instant the speed of the elevator, as well as that of the woman, is 10 m/s and both are decreasing at the rate of 2 m/s2. At that instant, the floor of the elevator exerts a force on the woman that is

about 400 N, pointing up

Which of the following statements about acceleration is FALSE?

an object that is accelerating is going too fast

The left tip of a wind turbine blade accelerates upward, as you view it. By the right-hand rule, the torque on the wind turbine is pointing

away from you

The x-component of a particle's velocity is sampled every 0.5 s. The data are fit with a straight line as shown in the v versus t plot. Assuming the fit is a good approximation to the motion, which of the force versus time plots best represents the x-component of the net force on the particle as a function of time?

b

A mass is hanging from the end of a horizontal bar which pivots about an axis through it center, but is being held stationary. The bar is released and begins to rotate. As the bar rotates from horizontal to vertical, the magnitude of the torque on the bar

decreases

A skier skis in a straight line down a hill gradually picking up speed as he goes. Which of the following could plausibly be an external force diagram for the skier during this motion? Assume air resistance is negligible.

diagram d

In the figure, what does the spring scale read? The pulleys are ideal and the strings and scale are also massless.

exactly 1.0 N

The Moon is accelerated toward the earth, so it is gradually getting closer to the earth.

false

Uniform Circular Motion: The Moon is accelerated toward the earth, so it is gradually getting closer to the earth.

false

A bullet is fired horizontally from a rifle on the Moon (no air, g = 1.6 m/s2) with initial speed v0. Assuming a level and endless ground, which statement is false?

false: The flight time increases as v0 increases. true: The bullet moves along a parabolic path. During the flight, the minimum speed of the bullet is v0. During its entire flight the acceleration is constant.

An astronaut goes out for a "space-walk" at a distance above the earth equal to the radius of the earth. What is her acceleration due to gravity at that point?

g/4

Weight and g: An astronaut goes out for a "space-walk" at a distance above the earth equal to the radius of the earth. What is her acceleration due to gravity at that point?

g/4

When an ice-skater who is doing a spin pulls her arms in

her angular momentum remains constant but her angular speed increases.

Kepler's Laws: Halley's Comet is in a highly elliptical orbit around the sun. Therefore the orbital speed of Halley's Comet, while traveling around the sun,

increases as it nears the sun

If no external forces are acting on a moving object

it will continue with the same velocity

A child is riding a bike and skids to a stop. What happens to their kinetic energy?

its converted into thermal energy

The quantities remain constant in an inelastic collision are

momentum, but neither kinetic energy nor temperature.

Jim is running slowly along a long straight path, but speeds when a dog starts following him. Which of the position versus time graphs shown could represent his motion?

only 3 and 4

Which of the following statements about velocity and/or speed are always TRUE? (1) Velocity is a vector quantity and speed is a scalar quantity. (2) The average velocity of an object on a round-trip journey would be 0. (3) Person X moves from location A to location B in 5 seconds. Person Y moves between the same two locations in 10 seconds. The speed of person X is twice that of person Y. (4) Person X moves from location A to location B in 5 seconds. Person Y moves between the same two locations in 10 seconds. The velocity of person X is twice that of person Y.

only statements 1,2 and 4 are true

Which of the following statements about distance and/or displacement are TRUE? (1) Distance is a vector quantity and displacement is a scalar quantity. (2) If a person walks in a straight line and never changes direction, then the distance and the magnitude of the displacement are exactly the same. (3) The diagram below depicts the path of a person walking from position A to B back to C to and then to D. The distance traveled is 90 yds. (4) For the same diagram below, the displacement of the person walking from A to B to C to D is 50 yds.

only statements 2 and 3 are true

The positions of two blocks at successive 0.20-second time intervals are represented by the numbered squares in the figure below. The blocks are moving towards the right. Are the blocks accelerating?

only the upper block is accelerating

A skater who is spinning and throws her arms out slows down because

she makes her rotational mass or moment of inertia bigger.

Two cars move towards each other on a frictionless road as shown in the sketch below. The two cars collide and immediately come to a standstill. During the collision, the total momentum of the two vehicles will

stay constant

Suppose Larissa throws a ball up in the air and it comes back down to the same place she threw it from. Ignore the times when the ball is in contact with her hand, and ignore air resistance.

the ball has a minimum kinetic and maximum potential energy at maximum height

A block and a rod are joined together. Each object is of uniform density. The center of mass of the combined object is at the position shown by the "X."Which has the greater mass, the block or the rod?

the block has a greater mass

In an inertial frame, an object cannot remain at rest unlesswhich of the following holds?

the net force acting on it is zero

A box is at rest on a flat table. Which of the following is true?

the normal force and the gravitational force are equal in magnitude and opposite in direction

Two identical bowling balls are moving down a bowling alley so that their centers of mass have the same velocity, but one just slides down the alley, while the other rolls down the alley. Which ball has more energy?

the rolling ball

Satellite Motion: Satellite A has twice the mass of satellite B, and moves at the same orbital distance from Earth as satellite B. Compare the speeds of the two satellites.

the speed of B is equal to the speed of A

An object is thrown straight up. At the top of its path

the velocity is zero and the acceleration is equal to g pointing down.

Newton's 3rd law is also called the law of action and reaction. The "reaction" force does not cancel the "action" force because

they act on different bodies

Suppose you are spending your weekend on roller skates trying to get momentum from somewhere. Which of the following will give you momentum in the north direction?

throwing your keys southward

You are riding an amusement park ride where you are strapped to the inside of a giant metal wheel. During some time interval the wheel is horizontal and rotating uniformly and rapidly. During this time interval your acceleration is

towards the center of the wheel

Is it possible to have motion in the absence of a net force?

yes

An object with mass m moves through free space with constant velocity. The magnitude of the force required to maintain this motion is equal to

zero