physics chapter 7 – Flashcards

The work that is done when twice the load is lifted twice the distance is _______.

When one does twice the work in twice the time, the power expended is _______.

When you lift twice the load twice as high, in half the time, the increase in potential energy is _______.

When traveling twice as fast your kinetic energy is increased _______.

Energy cannot be _______.

In a simple machine, how much work is done when an input of 10 N acts over a distance of 5 m?

Recycled energy is mainly _______.

The single requirement of all living things is _______.

Fossil fuels, hydroelectric power, and wind power ultimately get their energy from _______.

If you push for a half hour or a whole hour against a stationary wall

If you push an object a given distance, while applying twice the force, you do

A job is done slowly, while an identical job is done quickly. Both jobs require the same amount of work, but different amounts of

The power required to exert 1 N force, over a distance of 1 m in 1 second is

If an object is raised twice as high, its potential energy will be

An object that has kinetic energy must be

A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally have a kinetic energy that is

When properly used, a hydraulic press, like a wheel and axle, is capable of multiplying force input.

A ball rolling down an incline has its maximum kinetic energy at

A ball rolling down an incline has its minimum speed

Both a 50-kg sack is lifted 2 meters from the ground and a 25-kg sack is lifted 4 meters in the same time. The power expended in raising the 50-kg sack is

A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground?

Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed to do this job was

A car moves 4 times as fast as another identical car. Compared to the slower car, the faster car has

A machine puts out 100 Watts of power for every 1000 Watts put into it. The efficiency of the machine is

Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr?

A 2500-N pile-driver ram falls 10 m and drives a post 0.1 m into the ground. The average impact force on the ram is...

A car that travels twice as fast as another when braking to a stop will skid

How many Joules of energy are in one kilowatt-hour?

A flower pot of mass m falls from rest to the ground below, a distance h. Which statement is correct? The speed of the pot when it hits the ground depends on m. The KE of the pot when it hits the ground is proportional to h. The KE of the pot when it hits the ground does not depend on m. The speed of the pot when it hits the ground is proportional to h. None of these are correct.

Calculate the work done in lifting a 420-N barbell 1.8 m above the floor. Work = force × distance: W=Fd

What is the gain of potential energy of the barbell when it is lifted to this height?

Calculate the power expended when a 600-N barbell is lifted 2.4 m in 2.2 s. Power = work/time: P=W/t

Calculate the change in potential energy of 7.8×106 kg of water dropping 50 m over Niagara Falls. Gravitational potential energy = weight × height: PE = mgh

Calculate the kinetic energy of a 3.8-kg toy cart that moves at 7.0 m/s . Kinetic energy = (1/2)mass × speed^2 : KE = (1/2)mv^2

In raising a 5800-N piano with a pulley system, the workers note that for every 2.3 m of rope pulled downward, the piano rises 0.17 m . Ideally, find the force that is required to lift the piano.

Emily holds a banana of mass m over the edge of a bridge of height h. She drops the banana and it falls to the river below. Use conservation of energy to find the speed of the banana just before hitting the water.

Nellie Newton applies a force of 48 N to the end of a lever, which is moved a certain distance. If the other end of the lever moves one-third as far, find the force it exerts.

How much work is done when you push a crate horizontally with 120 N across a 7.0-m factory floor?

If the force of friction on the crate is a steady 70 N, find the KE gained by the crate.

Find the energy turned into heat.

This question is typical on some driver's license exams: A car moving at 50 km/h skids 15 m with locked brakes. How far will the car skid with locked brakes at 120 km/h?

A bullet has more kinetic energy than the recoiling rifle from which it is fired is because the force on the bullet acts over a...

If a ping pong ball and a golf ball are both moving in the same direction with the same amount of kinetic energy, the speed of the ping pong ball must be

A piece of taffy slams into and sticks to another identical piece of taffy that is at rest. The momentum of the two pieces stuck together after the collision is the same as it was before the collision, but this is not true of the kinetic energy, which is partly turned into heat. What percentage of the kinetic energy is turned into heat?

Two identical objects in outer space have a head-on collision and stick together. If, before the collision, one had been moving at 2 m/s and the other at 1 m/s, their combined speed after the collision would be

A 1-kg ball dropped from a height of 2 m rebounds only 1.5 m after hitting the ground. The amount of energy converted to heat is about

If several balls are thrown straight up with varying initial velocities, the quantity that will have the same value for each trial is the ball's

A popular swinging-balls apparatus consists of an aligned row of identical elastic balls that are suspended by strings so they barely touch each other. When two balls are lifted from one end and released, they strike the row and two balls pop out from the other end. If instead one ball popped out with twice the speed of the two, this would be a violation of conservation of

When a rifle is fired, it recoils as the bullet is set in motion. The rifle and bullet ideally acquire equal...