physics S1 final

Three objects are moving along a straight line as shown in the figure. Taking the positive direction to be to the right, what is the total momentum of this system?

-14.0 kg • m/s

If 4.0 J of work are performed in stretching an ideal spring with a spring constant (force constant) of 2500 N/m, by what distance is the spring stretched?

.057 m

a horizontal 52 N force is needed to slide a 50 kg box across a flat surface at a constant velocity of 3.5 m/s. what is the coefficient of kinetic friction between the box and the floor

.11

It requires 0.30 kJ of work to fully drive a stake into the ground. If the average resistive force on the stake by the ground is 828N how long is the stake?

.36m

A 1.0-kg object moving in a certain direction has a kinetic energy of 2.0 J. It hits a wall and comes back with half its original speed. What is the kinetic energy of this object at this point?

.50 J

A 35-N bucket of water is lifted vertically 3.0 m and then returned to its original position. How much work did gravity do on the bucket during this process?

0 J

A 0.14-kg baseball is dropped from rest from a height of 2.0 m above the ground. What is the magnitude of its momentum just before it hits the ground if we neglect air resistance?

0.88 kg • m/s

A 320-g air track cart traveling at 1.25 m/s suddenly collides elastically with a stationary 270-g cart. What is the speed of the 270-g cart just after the collision?

1.36 m/s

An object hits a wall and bounces back with half of its original speed. What is the ratio of the final kinetic energy to the initial kinetic energy of the object?

1/4

A 900-kg car traveling east at 15.0 m/s suddenly collides with a 750-kg car traveling north at 20.0 m/s. The cars stick together after the collision. What is the speed of the wreckage just after the collision?

12.2 m/s

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?

12P

an object that weighs 75 N is pulled on a horizontal surface by a horizontal pull of 50 N to the right. the friction force on this object is 30 N to the left. What is the acceleration of the object.

2.6 m/s2

How many joules of energy are used by a 1.0-hp motor that runs for 1.0 hour? (1 hp = 746 W)

2.7 MJ

a 400 kg box is lifted vertically upward with constant velocity by means of two cables pulling at 40.0 degrees on either side of the vertical direction. what is the tension in each cable

2560 N

two dogs, Rover and Fido, run on a level frictionless surface. Rover runs eastward with a momentum of 24 kg . m/s, and Fido runs northward with momentum 10 kg . m/s. They make a sudden perfectly inelastic collision. What is the magnitude of their combined momentum after the collision?

26 kg . m/s

How much kinetic energy does a 0.30-kg stone have if it is thrown at 44 m/s

290 J

A block of mass m = 34 kg and speed V is behind a block of mass M = 81 kg and speed of .50 m/s as shown in the figure. The surface is frictionless and the blocks collide and couple. After the collision, the blocks have a common speed of .90m/s What is the magnitude of the impulse on the 34-kg block due to the collision?

32 N • s

what magnitude net force is required to accelerate a 1200 kg car uniformly from 0 m/s to 27.0 m/s in 10.0 s

3240 N

A 0.10-kg ball, traveling horizontally at 25 m/s, strikes a wall and rebounds at 19 m/s. What is the magnitude of the change in the momentum of the ball during the rebound?

4.4 kg • m/s

a person is using a rope to lower a 5.0N 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

5.0N

A net force of 125 N is applied to a certain object. As a result, the object accelerates with an acceleration of 24.0 m/s2. The mass of the object is

5.21 kg

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

Matthew pulls his little sister Sarah along the horizontal ground in a wagon. He exerts a force on the wagon of 60.0 N at an angle of 37.0° above the horizontal. If he pulls her a distance of 12.0 m, how much work does Matthew do?

575 J

Calculate the impulse due to a force of 4.5N that lasts for 1.4s

6.3 kg• m/s

A 1200-kg car moving at 15.6 m/s suddenly collides with a stationary car of mass 1500kg. If the two vehicles lock together, what is their combined velocity immediately after the collision?

6.9 m/s

a truck is using a hook to tow a car whose mass is one quarter that of the truck. if the force exerted by the truck on the car is 6000 N, then the force exerted by the car on the truck is

6000 N

An astronaut weighs 99.0 N on the Moon, where the acceleration of gravity is 1.62 m/s2. How much does she weigh on Earth?

600N

a 1200 kg car is pulling a 500kg trailer along level ground. friction of the road on the trailer is negligible. the car accelerates with an acceleration of 1.3 m/s2. what is the force exerted by the car on the trailer

650 N

what is the mass of an object that experiences a gravitational force of 685N near Earth's surface where g=9.81 m/s2

69.8 kg

If I weigh 741 N on Earth at a place where g = 9.80 m/s2 and 5320 N on the surface of another planet, what is the acceleration due to gravity on that planet?

70.4 m/s2

How much work would a child do while pulling a 12-kg wagon a distance of 4.2m with a 22N force?

95J

Person X pushes twice as hard against a stationary brick wall as person Y. Which one of the following statements is correct?

Both do zero work.

You slam on the brakes 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 the same conditions?

It would have skidded 4 times farther.

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

Neither of them does any work.

inside of a train a ball of weight is hanging by a light wire at rest from the ceiling. the wire makes an angle with the ceiling, as show in the figure. which one of the following conditions must be true about the tension in the wire

T sin e = W

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

A very elastic rubber ball is dropped from a certain height and hits the floor with a downward speed v. Since it is so elastic, the ball bounces back with the same speed v going upward. Which of the following statements about the bounce are correct?

The magnitude of the ball's momentum was the same just before and just after the bounce.

A stone can slide down one of four different frictionless ramps, as shown in the figure. For which ramp will the speed of the ball be the greatest at the bottom?

The speed of the ball will be the same for all ramps.

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

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

You throw a baseball straight up. Compare the sign of the work done by gravity while the ball 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.

A lightweight object and a very heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill with no air resistance. Which object rises to a greater height?

They both slide to exactly the same height.

In a collision between two unequal masses, which mass receives a greater magnitude impulse?

They receive equal impulses.

a 75N box rests on a perfectly smooth (no friction) horizontal surface. The minimum force need to start the box moving is

any horizontal force greater than zero

The graphs shown show the magnitude F of the force exerted by a spring as a function of the distance x the spring has been stretched. For which one of the graphs does the spring obey Hooke's law?

b

In a game of pool, the white cue ball hits the #5 ball and stops, while the #5 ball moves away with the same velocity as the cue ball had originally. Both balls have the same mass. This type of collision is: (Assume they have the same mass)

elastic.

a horse pulls a cart with force. as a result of this force the cart accelerates with a constant accleeration. The magnitude of the force that the cart exerts on the horse

equal to the magnitude of force

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

an object of weight is in freefall close the the surface of earth. the magnitude of the force that the object exerts on earth is

equal to weight

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

exactly 1.0N

In an inelastic collision involving an isolated system, the final total momentum is

exactly the same as the initial momentum.

Impulse is the change in force.

false

In innelastic collisions energy is conserved.

false

a box is placed on a table which rests on floor. The box pushes on the table; the reaction force to the box's push on the table is the table's push on the floor.

false

a golf club hits a golf ball with a force 2400 N, sending the ball into the air. The force exerted on the club by he ball must be less than 2400 N or else the ball would not have moved forward

false

in order to get an object moving, you must push harder on it than it pushes back on you

false

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

four times Jack's power output.

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.

The momentum of an isolated system is conserved

in both elastic and inelastic collisions.

A railroad car collides with and sticks to an identical railroad car that is initially at rest. After the collision, the kinetic energy of the system

is half as much as before.

a person who normally weighs 700N 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 700N

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 moons surface, compared to earth

mass is the same, weight is less

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

Two friends are standing on opposite ends of a canoe that is initially at rest with respect to a frictionless lake. The person in the front throws a very massive ball toward the back, and the person in the back catches it. After the ball is caught (1 min later), the canoe is

stationary.

A rubber ball and a lump of clay have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The clay sticks to the wall. Which one of these objects experiences the greater momentum change?

the ball

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

the net force on the object is zero

an onject 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 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

if you pound a feather with a hammer, which one feels a greater force

the size of the force is always exactly the same on both of them

you are standing in a moving bus, facing forward, when you suddenly slide forward as the bus comes to an immediate stop. what forced caused you to slide forward

there is not a force causing you to slide forward.

In elastic collisions energy is conserved

true

Momentum is always conserved when objects collide.

true

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 55 kg box rests on a horizontal surface. the coefficient of static friction between the box and the surface is .30. a horizontal 140N is applied to the box. what is the friction force on the box.

140N

A traveler pulls on a suitcase strap at an angle 36° above the horizontal. If 555J of work are done by the strap while moving the suitcase a horizontal distance of 15m what is the tension in the strap?

46N

A block of mass m = 9.0 kg and speed V and is behind a block of mass M = 27 kg and speed of .50 m/s as shown in the figure. The surface is frictionless, and the blocks suddenly collide and couple. After the collision, the blocks have a common speed of 0.90 m/s. How much kinetic energy of the blocks is lost due to the collision?

8.6 J

A child does 350 J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope. The tree house is 4.0m above the ground. What is the mass of the box?

8.9 kg

Joe and Bill throw identical balls vertically upward. Joe throws his ball with an initial speed twice as high as Bill. If there is no air resistance, the maximum height of Joe's ball will be

four times that of Bill's ball.

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

greater than the weight of the elevator