Physics

Two air track gliders are held together with a string. The mass of glider A is twice that of glider B. A spring it tightly compressed between the gliders. If the gliders are initially at rest and the spring is released by burning the string, what is the total momentum of both Gliders after the release?

0

What is the rotational speed of the hand on a clock that measures the seconds?

0.0167 rev/s

The rectangular board in the figure is fixed but free to rotate about point P. Forces of equal magnitude are applied tot he board at the locations shown in cases 1 - 4. 1. ^ 2. ^ *P 3. < 4. <. In which case is the magnitude of the torque on the board the greatest?

1

Assume that two cars have the same kinetic energy, but the re car has twice the speed of the blue car. We then know that the red car has...

1/4 as much mass as the blue car

An elevator is moving downward and slowing down with an acceleration equal to one quarter that of gravity. If a person who weighs 800 N when at rest on Earth steps on a bathroom scale in this elevator, what will the scale read?

1000 N

A 3 kg toy with a speed of 8 m/s collides head on with a 2 kg car traveling in the opposite direction with a speed of 4 m/s. If the cars are locked together after the collision with a speed of 2 m/s, how much kinetic energy is lost? Kinetic energy lost = 1/2(3kg)(8m/s)^2 + 1/2(2 kg)(4 m/s)^2 - 1/2(3kg + 2kg)(2 m/s)^2 =

102 J

It takes about 30 s for a jet plane to go from rest to the takeoff speed of 100 mph(44.7m/s). What is the average horizontal force that the seat exerts on the back of a 80 kg passenger during takeoff?

119 N

A 55 kg person climbs is set of stair that are 2.5 m high determine the work done by the person against gravity.

1375 J

A child with a mass of 25 kg is riding on a merry go round. if the child has a speed of 3 m/s and is located 2 m from the center of the merry go round, what is the childs angular momentum?

150 kg*m^2/s

A child with a mass of 25 kg sits at a distance of 1.8 m from the pivot of a seesaw. Calculate the distance,from the pivot at which a 18 kg child should sit to balance the seesaw. Distance = 450 N / 18 kg (10 m/ s^2) =

2.5 m

Larry has a mass of 90 kg and runs across the front of the classroom with a speed of 5 m/s and jumps onto a giant skateboard. The skateboard is initially at rest and has a mass equal to larrys. If we ignore friction with the floor, what is the speed of larry and the skateboard?

2.5 m/s

Gorge run across the front of the classroom with a momentum of 300 kg*m/s and jumps onto a giant skateboard. The skateboard is initially at rest and has a mass equal to gorges. If we ignore the friction with the floor, what is the total momentum of gorge and the skateboard?

300 kg*m/s

A person with a weight of 720 on Earth travels in a spacecraft accelerating through space a long way from any massive objects. The acceleration of gravity on Earth can be taken to be 10 m/s^2 and the acceleration of the spacecraft is 4.2 m/s^2. Determine the persons apparent weight in the spacecraft. Apparent weight = Mass x geff = 72 x 4.2 m/ s^2

302 N

A radio controlled car increased its kinetic energy from 4 J to 12 J over a distance of 2 m. What was the average net force on a the car during this interval?

4 N

A child with a mass of 25 kg sits at a distance of 1.8 m from the pivot of a seesaw. Calculate the torque the child exerts on the seesaw, as measured with the respect to the pivot. Torque = 25 kg x 10 m/s^2 x 1.8 m =

450 N. m

If a hair dryer has 1500 W, how much energy does it require in 5 min?

450,000 J

If a sports car with a mass of 1000 kg travels fown the road with a speed of 30 m/s, it kinetic energy is...

450.000 J

Juan has amass of 60 kg and is standing on a giant skateboard that is initially at rest and has a mass of 30 kg. If we ignore frictional effects with the floor, what is the speed of the skateboard if Juan walks to the right with a speed of 3 m/s?

6 m/s

A 1800 kg car is traveling at 30 m/s around a curve with a radius 120 m. What is the angular momentum of the car?

6,480,000 kg*m^2/s

A person with a weight of 720 on Earth travels in a spacecraft accelerating through space a long way from any massive objects. The acceleration of gravity on Earth can be taken to be 10 m/s^2 and the acceleration of the spacecraft is 4.2 m/s^2. Determine the persons mass. Mass = W/ gravitational acceleration

72 kg

A 55 kg person climbs is set of stair that are 2.5 m high determine the gravitational potential energy the person gains .Gravitational potential energy gained = mg/\h = (55 kg)(10 m/s^2)(2.5m)

= 1375 J

A 5 kg cart moving at 2 m/s hits a stationary 5 kg cart. The two move off together at 1 m/s. Paula contends, momentum is conserved in this collision because the momentum of the system has the same value before and after the collision. Lillian counters, the momentum of the system before the collision is 10 kg*m/s, not zero, so momentum is not conserved, As a momexpert, you should...

Agree entirely with Paula; Lillians argument is irrelevant

During takeoff, the surface of the coffee you hold is no longer parallel to the floor of the airplane. Which of the following is correct?

The surface of the coffee tips forward because the upwards direction in your non -inertial reference system now points toward the ceiling and the front of the plane

What happens to the total momentum of a star that undergoes a supernova explosion?

It remains constant

A red car drives due north on the freeway at a constant speed of 60 mph.A blue car is located to the north of the red car. As measured in the reference system of the road, the velocity if the blue car is to the north, is less than 60 mph, and is steadily, decreasing in magnitude. In the reference system of the red car, the blue car is...

Moving to the south

Assume that you are riding in a windowless room on a perfectly smooth surface. Imagine that you have a collection of objects and measuring devices in the room. which of the following experiments could you do to prove that the room is moving horizontally at a constant velocity?

None on the above

A person drops a ball in a train traveling along a straight, horizontal tack at a constant velocity. what would the observer on the ground say about the horizontal forces acting on the ball?

There are no horizontal forces acting on the ball

A student conducts a race between a block sliding down a frictionless ramp and a hoop rolling without slipping down ramp. The block and the hoop each start from rest, and have the same mass. The two ramps have the same height and angle of incline. Which object wins the race?

block

What kind of motion does a constant, non zero torque produce on an object mounted on an axle?

constant rotational acceleration

An object have velocity toward the south.If a force directed toward the north acts on the object, it will initially cause the kinetic energy of the object to...

decrease

If the rockers are fired from an airplane in the forward direction, the momentum of the airplane will...

decrease

When a star undergoes supernova explosion, the total energy of the universe

does not change

A basketball is rolling directly south along a smooth gym floor. Using a wood baseball bat, you give the ball a brief tap such that the force is directed east. As a result of the tap the magnitude of the momentum of the ball....

increasw

A system consisting of two particles has 0 momentum. The kinetic energy of this system

may or may not be zero

A red car drives due north on the freeway at a constant speed of 60 mph. A blue car is located to the north of the red car, and is traveling due north at a constant speed of 40 mph. In the reference system of the red car, the blue car is...

moving with constant speed

A train is traveling along a straight horizontal track at a constant velocity of 50 mph. An observer in the train holds a ball directly over a white spot on the floor of the train. If she drops the ball,it will land...

on the white spot

Two flywheels have the same mass but one is much thinner than the other such that its radius is twice that of the smaller one. If both flywheels are spinning about their axes at the same rate, which one would be harder to stop?

the one with the larger radius

As the Apollo astronauts passed the point in space where the gravitational attraction of Earth and the moon on the spacecraft were equal,

they start to speed up.

Why is skiing into a wall of deep powder less hazardous to your health than skiing into a wall of bricks?

The increased stopping time in powder means a small stopping force

Which of the following physical quantities is not necessarily an invariant even if the system is close?

Volume

A student conducts a race between a block sliding down a frictionless ramp and a hoop rolling without slipping down ramp. The block and the hoop each start from rest, and have the same mass. The two ramps have the same height and angle of incline. In this race, the amount of potential energy lost by the hoop will be...

equal to that lost by the block

While you are standing on the ground, you observe your friends pass by in a an traveling at a constant velocity. They drop a ball and you all make measurements of the balls motion. Which of the following quantities has the same value in both reference systems?

forces

which of the following is NOT a potential energy?

friction

Clay stands on his bathroom scale in the morning and finds that he weighs 50 lbs. He takes a ride in the elevator that foes up the side of the space needle in Seattle. Much to the amusement of the other passengers, he brings his bathroom scale and stands on it during the ride. During the time that the elevator is accelerating upward, the reading on the scale is...

greater than 50 lbs

A clay ball and a rubber ball have equal mass. A student releases each ball from rest at the same height. The clay ball sticks to the ground while the rubber ball bounces back up. The magnitude of the impulse delivered to the rubber ball by the floor is...

greater than that delivered to the clay ball by the floor

A worker uses a wheelbarrow to lift a load of gravel. While standing at res, with only the wheel touching the ground, the magnitude of the force exerted by the gravel on the wheelbarrow is...

greater than that exerted by the worker.

A fully loaded trailer truck is less stable than a race car because the truck...

has a higher center of mass