Ap Physics

A car goes around a curve of radius r at a constant speed v. Then it goes around a curve of radius 2r at speed v. What is the centripetal force on the car as it goes around the second curve, compared to the first?

1/2 as big

If a car goes around a curve at half the speed, the centripetal force on the car is

1/4 as big

A bullet is fired horizontally and hits the ground in 0.5s. If it had been fired with twice the speed in the same direction, it would've hit the ground in...

0.5s. (height determines time, speed determines distance)

A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that the hill exerts on the sled parallel to the surface of the hill?

120 N

An airplane moves at 141 km/hr towards the northeast (45º). What is its component of velocity in the northward direction?

141sin(45)=x x=99.7km/hr (aka 100)

A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that the surface of the hill exerts on the sled?

160 N

A car is moving with a constant speed v around a level curve. The coefficient of friction between the tires and the road is 0.40. What is the minimum radius of the curve if the car is to stay on the road?

2.5v^2/g

When you drop a pebble from height H, it reaches the ground with kinetic energy K if there is no air resistance. From what height should you drop it so it will reach the ground with twice as much kinetic energy?

2H

A force produces power P by doing work W in a time T. What power will be produced by a force that does six times as much work in half as much time?

2P

Milo does twice as much work as Marvin does and in half the time. Milo's power output is

4 times margins output

When you drop a pebble from height H, it reaches the ground with speed V if there is no air resistance. From what height should you drop it so it will reach the ground with twice speed?

4H

A very light wire is used to hang a series of 8.0 kg bricks. This wire will break if the tension in it exceeds 450 N. The bricks are hung one below the other from a hook in the ceiling using this wire, as shown in the figure. *Use 10 m/s2 for acceleration due to gravity. How many whole bricks can be hung without breaking the wire?

5 10x8=80 450/80= 5

A person is using a rope to lower a 5.0 N bucket into a well with a constant speed of 2.0 m/s. What is the magnitude of the force exerted by the rope on the bucket?

5.0 N

Which requires more work, increasing a car's speed from 0 mph to 30 mph or from 50 mph to 60 mph?

50 mph to 60 mph

What minimum banking angle is required for an olympic bobsled to negotiate a 100-m radius turn at 35 m/s without skidding? (Ignore friction.)

51º

A block of mass m is pushed up against a spring, compressing it a distance x, and is then released. The spring projects the block along a frictionless horizontal surface, giving the block a speed v. The same spring projects a second block of mass 4m, giving it a speed 3v. What distance was the spring compressed in the second case?

6x

An object moving with constant speed in a circular path experiences

Centripetal acceleration

When a ball is thrown upward with no air resistance, the acceleration at the highest point is...

Downward

A football is kicked into the air @ an angle of 45º with the horizontal. At the very top of the ball's path, its velocity is

Entirely horizontal

A football is kicked into the air @ an angle of 45º with the horizontal. At the very top of the ball's path, its acceleration is

Entirely vertical

A bucket is being lowered by a very light rope with a constant downward velocity. The tension in the rope must be

Equal to the weight of the bucket

A 10-kg rock and a 20-kg rock are thrown upward with the same initial speed Vo and experience no significant air resistance. If the 10-kg rock reachers a maximum height H, what maximum height will the 20-kg rock reach?

Exactly H. Mass does not matter without air resistance.

A 10-kg rock and a 20-kg rock are dropped from the same height and experience no significant air resistance. If the 20-kg rock reaches the ground with a time T, what time will the 10-kg rock hit the ground?

Exactly T.

Suppose a ball is thrown straight up and experiences no appreciable air resistance. What is its acceleration just before it reaches its highest point?

Exactly g

If the velocity versus time graph of an object is a straight line with a non-zero slope with the time axis, the object is...

Moving with a constant nonzero acceleration

Two men, Milo and Marvin, push against a car that has stalled, trying unsuccessfully to get it moving. Marvin stops after 10 min, while Milo is able to push for 5.0 min longer. Compare the work they do on the car.

Neither does any work

A rope, tied between a motor and a crate, can pull the crate up a hill of ice (assume no friction) at constant velocity. The free-body diagram of the crate should contain

three forces

A car goes around a curve of radius r at a constant speed v. Then it goes around a curve of radius 2r at speed 2v. What is the centripetal acceleration on the car as it goes around the second curve, compared to the first?

twice as big

Swimmers at a water park have a choice of two frictionless water slides, as shown in the figure. Although both slides drop over the same height h, slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed v1 of a swimmer reaching the bottom of slide 1 compare with v2, the speed of a swimmer reaching the end of slide 2?

v1=v2

A block of mass m is initially moving to the right on a horizontal frictionless surface at a speed v. It then compresses a spring of spring constant k. At the instant when the kinetic energy of the block is equal to the potential energy of the spring, the spring is compressed a distance of:

v√(m/2k)

A roller coaster car (mass = M) is on a track that forms a circular loop (radius = r) in the vertical plane. If the car is to just maintain contact with the track at the top of the loop, what is the minimum value for its speed at that point?

√gr

A coin of mass m rests on a turntable a distance r from the axis of rotation. The turntable rotates with a frequency of f. What is the minimum coefficient of static friction between the turntable and the coin if the coin is not to slip?

(4π^2f^2r)/g

If the velocity is zero at one instant, what is true about the acceleration of the object?

-Acceleration could be positive -Acceleration could be negative

The slope of a velocity versus time graph gives...

Acceleration

A 1 kg banana is released from a height of 6 m, and a 2 kg banana is released from a height of 3 m. Air resistance is negligible as they fall. Which of the following statements about these bananas are correct?

As they reach the ground, the 1-kg banana will be moving faster than the 2-kg and both will have the same kinetic energy

At what point in its path is the vertical component of velocity the smallest?

At the top

A heavy dart and a light dart are launched horizontally on a frictionless table by identical ideal springs. Both springs were initially compressed by the same amount. Which of the following statements about these darts are correct?

Both darts have the same KE just as they move free of the spring, the lighter dart leaves the spring moving faster than the heavy dart, both darts had the same initial elastic potential energy.

A 4.0 kg object is moving with speed 2.0 m/s. A 1.0 kg object is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before stopping?

Both objects travel the same distance

You and your friend, who weighs the same as you, 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 of you and your friend, after you both reach the top.

Both of you have the same gravitational potential energy at the top.

A heavy sled and a light sled, both moving horizontally with the same speed, suddenly slide onto a rough patch of snow and eventually come to a stop. The coefficient of kinetic friction between the sleds and the rough snow is the same for both of them. Which of the following statements about these sleds are correct?

Both sleds will slide the same distance in the snow before stopping and the friction from the snow will do more negative work on the heavier sled than the lighter sled.

A woman is straining to lift a large crate of bananas, but without success because it is too heavy. We denote the forces on the crate as follows: F is the magnitude of the upward force being exerted on the crate by the person, N is the magnitude of the vertical contact force on the crate by the floor, and mg is the weight of the crate. How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate?

F+N=mg

If the velocity of an object is zero, the object cannot be accelerating. True or False?

False, gravity exists

If the velocity of an object is zero at some point, then its acceleration must also be zero at that point. True or False?

False, gravity exists at all times

During the investigation of a traffic accident, police find skid marks 90 m long. They determine the coefficient of friction between the car's tires and the roadway to be 0.5 for the prevailing conditions. To find the speed of the car you must

Find the acceleration of the car

A stone is held at a height h above the ground. A second stone with four times the mass of the first one is held at the same height. The gravitational potential energy of the second stone compared to that of the first stone is

Four times as much

An elevator suspended by a vertical cable is moving downward but slowing down. The tension in the cable must be

Greater that the weight of the elevator

A bullet shot horizontally from a gun..

Hits the ground at the same time a bullet dropped vertically will hit the ground.

If you ignore the air resistance of a projectile in motion, the ____________ of the projectile remains constant.

Horizontal component of the velocity vector

A car goes around a curve of increasing radius. What happens to the centripetal force on the car?

It decreases

At what point in its path is the horizontal component of velocity the smallest?

It is the same throughout the path

A golfer drives her ball from the tee down the fairway in a high arching shot. When the ball is at the height of its flight...

Its velocity and acceleration are both nonzero (its vertical velocity is 0, but its horizonatl component is nonzero.)

A ball is thrown straight up, reaches a maximum height, then falls to its initial height. Which of the following statements about the direction of the velocity and acceleration of the ball going up is correct?

Its velocity points upward and its acceleration points downward

A truck has four times the mass of a car and is moving with twice the speed of the car. If Kt and Kc refer to the kinetic energies of truck and car respectively, it is correct to say that

Kt=16Kc

A person who normally weighs 700 N is riding in an elevator that is moving upward but slowing down at a steady rate. If this person is standing on a bathroom scale inside the elevator, what would the scale read?

Less than 700

A heavy dart and a light dart are launched vertically by identical ideal springs. Both springs were initially compressed by the same amount. There is no significant air resistance. Which of the following statements about these darts are correct?

Lighter dart goes higher and at the maximum height with darts have the same gravitational potential energy

The acceleration due to gravity is lower on the Moon than on Earth. Which one of the following statements is true about the mass and weight of an astronaut on the Moon's surface, compared to Earth?

Mass is the same but weight is less

A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The friction force on the box due to the floor is equal to

Pcosø

A stone of mass M is dropped from an airplane that has a horizontal velocity V at height H above a lake. If theres no air resistance, the horizontal distance R from the point on the lake directly below the point of release to the point where the stone strikes the water is given by which formula?

R=v√(2h/g)

Roll a bowling ball of the edge of a table. As it falls, its horizontal component of velocity...

Remains constant

An object is undergoing free fall motion. As it falls, the object's...

Speed increases

Inside of a truck a ball of weight mg is hanging by a light wire at rest from the ceiling. The wire makes an angle ø with the ceiling, as shown in the figure. Which one of the following conditions must be true about the tension T in the wire?

Tcosø=mg

Brick A is dropped from the top of a building. Brick B is thrown straight down from the same building, and neither one experiences appreciable air resistance. Which statement about their accelerations is correct?

The 2 bricks have the exact same acceleration.

Which one has larger kinetic energy: a 500 kg object moving at 40 m/s or a 1000 kg object moving at 20 m/s?

The 500-kg object (1/2mv^2)

Suppose that an object travels from one point in space to another. Make a comparison between the magnitude of the displacement and the distance traveled by the object.

The displacement is either less than or equal to the distance traveled

When a 45 kg person steps on a scale in an elevator, the scale reads a steady 480 N. Which of the following statements must be true?

The elevator is accelerating upward at a constant rate and from the given information we cannot tell if it is moving up or down

A bomber flying in level flight with constant velocity drops a bomb before its over the target. Neglecting air resistance, which of the following isn't true?

The horizontal velocity of the plane equals the vertical velocity of the bomb as it is dropped.

An object is moving with constant non-zero velocity. Which of the following statements about it must be true?

The net force the object is zero

An object of mass m rests on a flat table. The earth pulls on this object with a force of magnitude mg. What is the reaction force to this pull?

The object is pulling upward on the earth with force MG

You push on box G that is next to box H, causing both boxes to slide along the floor, as shown in the figure. The reaction force to your push is

The push of box G against you

An object moves in a circular path at a constant speed. Consider the direction of the object's velocity and acceleration vectors.

The vectors are perpendicular

If the force on an object is in the negative direction, the work it does on the object must be

The work could either be positive or negative, depending on the the direction the object moves

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

The work is negative on the way up and positive on the way down.

You are standing in a moving bus, facing forward, when you suddenly slide forward as the bus comes to an immediate stop. What force caused you to slide forward?

There is not a force causing you to slide forward

Two objects are thrown from the top of a tall building. One is thrown up, and the other is thrown down, both with the same initial speed. What are their speeds when they hit the street? Neglect air resistance.

They're traveling at the same speed

(cont.) If you add one more brick to the number found in 16, which string will break?

Top wire has the most tension

A car goes around a curve of radius r at a constant speed v. What is the direction of the net force on the car?

Toward the curves center

A baseball is thrown with a velocity V and an angle ø with the horizontal. The horizontal component of its velocity is...

Vcosø

The slope of a position versus time graph gives...

Velocity

A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The normal force on the box due to the floor is equal to

W+Psinø

When is the average velocity of an object is equal to instantaneous velocity?

When Velocity is constant

The area under the curve, on a Force versus position (F vs. x) graph, represents

Work

A packing crate slides down an inclined ramp at constant velocity. Thus we can deduce that

a frictional force is acting on it

A toolbox, of mass M, is resting on a flat board. 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 µ

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=mgcosø

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 force of static friction f on the block?

f=mgsinø

Two boxes P and Q on a perfectly smooth horizontal surface are connected by a light horizontal cord. The mass of P is greater than that of Q. A horizontal force is applied to box Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P is

less than F but not zero

A pilot executes a vertical dive, and then follows a semi-circular arc until it is going straight up. Just as the plane is at its lowest point, the net force on him is

more than mg, pointing upward

A car of mass m goes around a banked curve of radius r with speed v. If the road is frictionless due to ice, the car can still negotiate the curve if the horizontal component of the normal force on the car from the road is equal in magnitude to

mv^2/r

If the units of your answer are kg ∙ m2/s3, which of the following types of quantities could your answer be?

power

You are in a train traveling on a horizontal track and notice that a piece of luggage starts to slide directly toward the front of the train. From this observation, you can conclude that this train is

slowing down

An object is placed on an inclined plane. The angle of incline is gradually increased until the object begins to slide. The angle at which this occurs is θ. What is the coefficient of static friction between the object and the plane?

tanø

Two objects, one of mass m and the other of mass 2m, are dropped from the top of a building. If there is no air resistance, when they hit the ground

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

A 5 kg block and a 10 kg block slide down a frictionless incline and

they both have the same acceleration