Practice!

Sample Problem

A roller coaster of mass 2000 kg is rolling down a track with an instantaneous speed 10m/s. What is its kinetic energy?

Joules

Solution

We will use the formula KE = 1/2 mv2. We are given that m = 2000, and v = 10. We can plug these values in to get KE = 1/2 (2000) (10) 2 = 100,000 = 1 × 105 Joules.