1. Kinetic Energy

Learning outcomes
  • I can define kinetic energy as the energy associated with motion.
  • I can explain how an object's mass and speed affect its kinetic energy.
  • I can recall and use the equation\( E_k = \frac{1}{2}mv^2 \) .
  • I can calculate the kinetic energy of moving objects in a variety of situations.
  • I can analyze how changes in speed affect kinetic energy and explain why kinetic energy increases rapidly with velocity.

Kinetic Energy

The amount of kinetic energy in a moving object can be calculated using the equation: 

Ek=½m v2 

where

  • Ek is measured in joules (J) 
  • m is mass measured in kilograms (kg)
  • v is speed measured in metres per second (m/s) 

An apple of mass 100 g falls from a tree. It reaches a speed of 6 m/s before landing on Isaac’s head. What is the gain of kinetic energy of the apple? 

List:

  • m = 100g = 0.1kg
  • v = 6 m/s
  • E = ?

Equation:

Ek=½m v2 

Solve:

E = 0.5(0.1)(6)2

E = 1.8J

 

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