Mass and Kinetic Energy

KE, PE, ME

Calculating Kinetic, Potential, and Total Mechanical Energy

Review: Kinetic Energy

KE = (0.5)(mass)(velocity²)

So kinetic energy is based on MASS and SPEED,

The unit for energy is J for Joules.

Multiple Choice

The faster an object moves, the ________ kinetic energy it has.

• more

• less

• none of the above

• all of the above

Multiple Choice

Which affects kinetic energy?

• mass

• speed

• height

• mass and speed

• mass and height

Multiple Choice

What is the unit for energy?

• kilogram (kg)

• meter (m)

• Newton (N)

• Joule (J)

Multiple Choice

Calculate the kinetic energy of a moving 4 kg object travelling at a velocity of 1 m/s.

• 2 J

• 4 J

• 20 J

• 40 J

Multiple Choice

What is the mass of a ball with a kinetic energy of 2000J, rolling at 10m/s?

• 50 kg

• 400 kg

• 40 kg

• 10,000 kg

Review: Gravitational Potential Energy

PE = (mass)(9.8)(height)

So gravitational potential energy is based on MASS and HEIGHT.

The unit for energy is J for Joules.

Multiple Choice

Choose the answer that has the most GRAVITATIONAL POTENTIAL energy.

• a 500 kg boulder on a 5 meter hill

• a 500 kg boulder on a 10 meter hill

• a 500 kg boulder on a 20 meter hill

Multiple Choice

What two factors affect GRAVITATIONAL POTENTIAL energy?

• mass

• height

• speed

• mass and speed

• mass and height

Multiple Choice

How could you increase the object's gravitational potential energy (GPE) without changing its distance from the ground (height)?

• Decrease the object's mass

• Increase the object's height

• Increase the object's mass

• Decrease the object's height

Multiple Choice

Which would have the LEAST gravitational potential energy (GPE)?

• A ball sitting on the ground

• Moon viewed from the Earth

• An airplane flying 30,000 feet above the ground

• A rock sitting on top of Mt. Everest

Multiple Choice

If the height is zero, gravitational potential energy

• is zero

• at its maximum

• 100J

• 200J

Multiple Choice

How much mass does a student have if they stand at a height of 1 meter and have 500 J of potential energy?

• 9.8 m/s^2

• 51 kg

• 10000 kg

• 490 kg

Review: Mechanical Energy

The total Mechanical Energy of a system is the potential energy + kinetic energy.

ME = PE + KE

The Law of Conservation Energy = The Mechanical Energy always stays constant.

The unit for energy is J for Joules.

Multiple Choice

At which point in the picture must the cart have the most MECHANICAL energy?

• Point 1

• Point 2

• Point 3

• They would all be the same

Multiple Choice

What is the MECHANICAL energy of the roller coaster car?

• 100 joules

• 50 joules

• 2500 joules

• 1 joule

Multiple Choice

What is the total Mechanical energy of a ball that has 2500 J of potential energy and 1000 J of kinetic energy?

• 2500 J

• 1000 J

• 1500 J

• 3500 J

Total Mechanical Energy is Conserved

If an object is at its highest point but not moving, then all the energy is potential. When it goes down, the potential energy is converted to kinetic energy.

The kinetic energy at a height of 0 will be equal to the potential energy the object had at the top.

PE initial = KE final

Multiple Choice

A 2 kg television is at a height of 1 meter. This makes its potential energy at the top 19.6 J. How much kinetic energy will it have at the bottom of a fall to the floor?

• 19.6 J

• 196 J

• 2 J

• 9.8J

Multiple Choice

You hold a 5 kg ball from a height of 2 m. How much mechanical energy does it have?

• 10 J

• 7 J

• 98 J

• 25 J

Multiple Choice

You drop a 5 kg ball from a height of 2 m. Just before it reaches the ground, how much kinetic energy does it have?

• 10 J

• 98 J

• 7 J

• 20 J

Multiple Choice

At which point is kinetic energy greatest? 

• W
• X
• Y
• Z

Multiple Choice

When a pendulum swings, at which point is potential energy at its greatest?

• 1 and 5

• 2 and 4

• 3

• 4 and 5

Multiple Choice

Where is kinetic energy at its maximum?

• a

• b

• c

• d

Multiple Choice

If a ball tossed into the air has a maximum gravitational potential energy of 5.75 joules, what is its maximum kinetic energy in the same toss?

• 5.75 joules

• 11.14 joules

• 2.88 joules

• 7.93 joules