Uniformly Accelerated Linear Motion Model: Energy

Physics 1: Section 3.4

If an object is approaching you, which of the following means it has more energy and is more concerning?

More massive

Moving faster

What is the formula for kinetic energy?

E _k = ½ mv²

What is kinetic energy?

The energy of an object associated with its motion and equal to one-half the product of the object’s mass and the square of the speed

Which of the following correctly defines the SI unit of kinetic energy?

J = kg x m² / s² (energy)

N = kg x m / s² (force)

kg x m / s (momentum)

The greater the force:

The greater the change in kinetic energy

The greater the displacement:

The greater the change in kinetic energy

Displacement without net force:

A ball rolling at constant velocity on a smooth floor

The net force is zero since the ball has constant velocity

The net work is zero

The kinetic energy does not change

Force without displacement:

Holding a heavyweight

The displacement is zero since the object does not move

Net work is zero

The kinetic energy does not change

If there is a net force, kinetic energy changes:

Greater force → greater increase (or decrease) in KE

If there is a displacement, kinetic energy changes:

Greater displacement → greater increase (or decrease) in KE

What is net work calculated as?

W_net = F_net,x Δx

What is net work defined as?

The transfer of energy that occurs when a net force has a component in the same or opposite direction of an object’s displacement

For linear motion with constant net force, net work is the product of the net force and the displacement

What is the symbol and SI unit for net work?

W_net and joule

If the network is in the same direction as the displacement, the net work is?

Positive

If the net force is negative and the displacement is positive, the net work is?

Negative

If the net force is positive and the displacement is zero, the net work is?

Zero

What is the Work-Energy Theorem equation?

W_net = E_K - E_K0

What does kinetic energy depend on?

Mass and speed

What does net work require?

Both a net force and a displacement

What does the sign of net work determine?

How kinetic energy and speed change