Mechanical Energy: Lesson 1

Why is a car crash so much more damaging at 60 mph than at 30mph? (Hint the speed is doubled)

When the speed is doubled, the kinetic energy of the car is quadrupled, NOT doubled. Refer to the equation.

Rotational Kinetic Energy

energy of an object due to its rotational motion

If the mass of an object is decreased by a factor of 1/2, kinetic energy decreases by a factor of ?

1/2

If the mass of an object is increased by a factor of 4, kinetic energy is increased by a factor of ?

4

If the mass of an object increases then the kinetic energy___________?

Increases

Formula for kinetic energy

KE=1/2mv^2

Motion Energy

Properly called kinetic energy. It is proportional to the mass of the moving object and grows with the square of its speed

The greater the mass

The greater the kinetic energy

What happens to the kinetic energy when the mass of a moving object increases?

The kinetic energy increases by the same factor as the mass increase

What happens to the kinetic energy of an object when its speed increases?

The kinetic energy increases by the square of the same factor as the speed increases. example: if the speed doubles, then 2^2, the kinetic energy quadruples (= 4). If the speed triples, then 3^2, the kinetic energy = 9

Translational Kinetic Energy

kinetic energy of an object as it moves from one location to another

The relationship between mass and kinetic energy is

proportional and linear