Chapter 9 Work and Energy

Define an inclined plane.

An inclined plane changes chances both the magnitude and the direction of the force.

True or false. Energy cannot be created or destroyed.

Energy cannot be created or destroyed is true.

Energy is transferred as what when mechanical energy decreases and temperature increases?

Energy is transferred as heat when mechanical energy decreases and temperature increases

How much work does a man perform if he pushes a crate along a factory floor and exerts a force of 55 N and moves the crate a distance of 4.0 m?

the work the man performs is 220 N.

A lever, screw, and a wheel and axel are all examples of what?

A lever, screw, and a wheel and axel are all examples of a simple machine.

A machine is a device than can do what?

A machine is a device that can multiply and change the direction of an input force.

A machine that is made up of more than one simple machine is called what?

A machine that is made up of more than one simple machine is called a compound machine.

The brakes on a car exert a frictional force of 6000 N in getting the car to stop. If the work done by the brakes is 120,000 J in coming to a stop, how many meters did the car travel after the driver applied the brakes?

After the driver applied the brakes, the car traveled 20 m.

All levers have a rigid arm that turns around a point called what?

All levers have a rigid arm that turns around a point called the fulcrum.

Energy that lies at the level of atoms and does not affect motion on a large scale is sometimes called what?

Energy that lies at the level of atoms and does not affect motion on a large scale is sometimes called non-mechanical energy.

True or false. A wheel an axel is an inclined plane?

False, a wheel and axel is not in inclined family.

If a medicine ball has a mass of 5 kg and is thrown with a speed of m/s, what is its kinetic energy?

If a medicine ball has a mass of 5 kg and is thrown with a speed of 2 m/s, its kinetic energy is 10 J.

True or false. If the kinetic energy of an object decreases, the non-mechanical energy will decrease.

If the kinetic energy of an object decreases, the non-mechanical energy will decrease is false.

Power is calculated by dividing work by what?

In order to calculate power you must divide work by time.

Is it true or false that both kinetic and potential energy are decreasing if a pendulum is swinging back and forth and has a kinetic energy of 400 J at a particular point in its path?

It's false that both kinetic and potential energy are decreasing if a pendulum is swinging back and forth and has a kinetic energy of 400 J at a particular point in its path.

True or false. Is potential energy an example of mechanical energy?

It's true that potential energy is an example of mechanical energy.

What is the energy of moving an object due to its motion?

Kinetic energy is the energy of moving an onject due to its motion.

Which of the following two energies are associated with atomic bonds, nuclear energy or potential energy?

Of the following, two energies, chemical energy is associated with atomic bonds.

Which of the two are examples of a wheel and axel, a nutcracker or a screwdriver?

Of the two, a screwdriver is an example of a wheel and axel.

A boy pushes on a parked car with a force of 200N. The car does not move. How much work does the boy do on the car?

Since the car did not move, the boy did zero work on the car.

What is the term used for the ability to do work?

The ability to do work is known as energy.

The efficiency of a ramp is 75%. If the amount of work input is 240 J, what is the amount of useful work output?

The amount of useful work output is 180 J.

True or false. The energy of a closed system is constant?

The energy of a closed system is constant is true.

True or false. The energy of an open system can increase.

The energy of an open system can increase is true.

How do you write the formula for calculating kinetic energy?

The formula used to calculate energy is KE=1/2mv squared.

What is the gravitational potential energy of a 54 kg box that is 8.0 m above the ground?

The gravitational potential energy of a 54 kg box that is 8.0 m above the ground is 4300 J.

What are the three things that gravitational potential energy depends on?

The height of the obejct, the acceleration due to gravity, and the mass of the object.

What is the mechanical advantage of a single fixed pulley?

The mechanical advantage of a single fixed pulley is 1.

What is the official SI unit for power>

The official SI unit for power is watt.

What requires the most work? a. A person holds a 1 kg weight still with outstretched arms. b. A person lifts a 1 kg weight 1 m off the floor.

The one that requires the most work is when a person lifts a 1kg wight 1 m off the floor.

What is the power of a weightlifter if he presses a 400N weight 0.5 over his head in 2 seconds?

The power of the weightlifter is 100 watts.

The primary source of the sun's energy is what?

The primary source of the sun's energy is nuclear fusion.

An object has a kinetic energy of 810 J after falling a certain distance. If the mass of the object is 20 kg, what is the speed of the object at this time?

The speed of the object at this time is 9 m/s.

What is the sum of the kinetic and potential energy of large-scale objects in a system called?

The sum of the kinetic and potential energy of large/scale objects in a system is called mechanical energy.

What is the term for an inclined plane wrapped around a cylinder?

The term for an inclined plane wrapped around a cylinder is a screw.

What is the term used for a quantity that measures how much a machine multiplies force or distance?

The term used for a quantity that measures how much a machine multiplies force or distance is mechanical advantage.

What do you call the stored energy resulting from the relative positions of objects in a system?

The term used for stored energy resulting from the relative positions of objects in a system is potential energy.

What is the term used for the ratio of useful work output to work input?

The term used for the ratio of useful work output to work input is efficiency.

An object weighing 75 N is dropped from the top of a building and falls at a distance of 28 m to the ground How much work does gravity do on the object from the time it's dropped to the time it hits the ground?

The work done by gravity from the time it's dropped to the time it hits the ground is 2100 J.

Which of the following is a compound machine: wheel and axel, pair of pliers, pulley or ramp?

They are all compound machines.

J, kg, m per second squared, N and mare units for what?

They are all units for work.

Watts, joules per second, and horsepower are all units of what?

They are all units of horsepower.

When a system exchanges energy with the environment outside the system, it's called what?

When a system exchanges energy with the environment outside the system, it's called an open system.

True or false. Work and energy are always equal?

Work and energy are always equal is false.

What is the term for the quantity that measures the effects of a force acting over a distance?

You call the quantity that measures the effects of a force acting over a distance work.

What do you call a quantity that measures the rate at which work is done?

You call the quantity that measures the rate at which work is done power.

What is the source of energy when dynamite explodes?

the source of energy when dynamite explodes is chemical energy.