Energy

How would you calculate an object's mechanical energy?

Add its kinetic and potential energies.

Describe the energy of a bowling ball as it rolls towards and hits a bowling pin.

As the ball rolls, it has energy, the ability to do work. When it hits the pins, it does work on them. During this process, some energy is transformed from the ball to the pins. After hitting the pins the ball has less energy and slows down.

If the pendulum is allowed to continue to swing, it will eventually come to a stop. Explain why.

As the pendulum swings it encounters friction, as a result, mechanical energy is converted into thermal energy.

Which letter represents the position at which the basketball has the greatest potential energy? Explain?

C, because at this point it is at its highest point and has all gravitational potential energy and no kinetic energy.

Which letter represents the position at which the basketball has the greatest kinetic energy? Explain.

E, because as the ball falls from C to E, potential energy is converted into kinetic energy and the velocity of the ball increase and attains its greatest velocity at point E.

A nuclear reaction in which the nuclei of atoms join together is called nuclear fission.

False; fusion

The kinetic energy of a book on a shelf is equal to the work done to lift the book to the shelf.

False; gravitational potential

Describe six different forms of energy. (Extra Credit)

Mechanical energy is energy associated with motion and position. Thermal energy is the total potential and kinetic energy of the particles in an object. Chemical energy is energy stored in chemical bonds that hold compounds together. Electrical energy is energy associated with moving charges, or electric current. Electromagnetic energy is the energy of radiation, including visible light and microwaves. Nuclear energy is stored in the nucleus of an atom.

Is the potential energy of the pendulum increasing or decreasing at position E? Explain.

Neither, at this point all of the balls energy is gravitational potential energy. It doesn't have kinetic energy because it is not moving.

Compare the sum of kinetic and potential energies of the pendulum at position A to the sum at position C. (Ignore friction.)

Point A is the greatest point of gravitational potential energy. Point C is the greatest point of kinetic energy.

How high must you lift a 25-newton book for it to have the same increase in potential energy as a 20-newton book that was lifted 0.5 m?

The 25 Newton book would need to be lifted 0.4 M in height to have an increase in gravitational potential energy of 10J. PE=NxM 20Nx0.5=10J J/N=M 10J/25N=0.4J

Explain why a thrown football has both potential and kinetic energy. What is the combined energy called?

The football has gravitational potential energy because of its position above ground. It has kinetic energy because it's moving. GPE+KE= Mechanical energy

A compressed spring has elastic potential energy.

True

In a machine, work output is less than work input because some energy is converted into thermal energy.

True

When work is done an object, the object gains energy.

True

An example of something that stores chemical energy is

a match.

Which of the following has kinetic energy?

a rolling bowling ball

What type of energy transformation is taking place when natural gas is used to heat water?

chemical energy into thermal energy

The law of _____________________________ states that energy cannot be created or destroyed.

conservation of energy

The ability to do work or cause change is called

energy.

If the velocity of an object is doubled, its kinetic energy is multiplied by

four.

Potential energy that depends on height is called

gravitational potential energy.

Energy is measured in units called

joules.

As water runs over a waterfall, its potential energy is converted into ____________________ energy.

kinetic

A large truck and a small car are moving at the same speed. The truck has greater kinetic energy because its __________ is greater.

mass

What type of energy does a spinning turbine have?

mechanical energy

Energy stored in the nucleus of an atom is called

nuclear energy.

The rate at which energy is transferred is called

power.

To maintain your body temperature, your body converts chemical potential energy into ______________ energy.

thermal