SPH4C Unit #3 – Energy Transformations

Kinetic Energy

Learning Goals and Success Criteria

Today I will be able to…

• Define the term kinetic energy

• Solve problems related to kinetic energy

Potential Energy

Let’s consider the wrecking ball situation again. When the ball is released, it falls. As the ball falls, its gravitational potential energy is gradually transformed into kinetic energy as its speed increases. Energy due to the motion of an object is called kinetic energy (Ek).

Kinetic Energy (Ek)• The energy possessed by a moving object

Kinetic Energy

A moving object has the ability to do work because it can apply a force to another object and displace it. The energy possessed by moving objects is called kinetic energy (Ek). For example, a moving hammer has kinetic energy because it has the ability to apply a force on a nail and push the nail into a piece of wood.

Kinetic Energy

In general, the kinetic energy of an object of mass, m, travelling at a speed, v, is given by the following formula:

Note:The faster the hammer moves or the greater its mass, the greater its kinetic energy, and the greater the displacement of the nail.

Kinetic Energy

Kinetic Energy (Ek)

• The energy possessed by a moving object.

Where Ek is the kinetic energy (J)

m is the mass (kg)v is the speed (m/s)

Kinetic Energy

Practice1. What is the kinetic energy of a 0.48 kg lawn dart travelling at a speed of

3.4 m/s?

Kinetic Energy

2. A softball with a mass of 0.17 kg has a kinetic energy of 98 J. What is its velocity?

Kinetic Energy

3. A 97 g cup falls from a kitchen shelf and shatters on the ceramic tile floor. Assume that the maximum kinetic energy obtained by the cup is 2.6 J and that air resistance is negligible.

a) Calculate the cup’s maximum speed.

Kinetic Energy

3. A 97 g cup falls from a kitchen shelf and shatters on the ceramic tile floor. Assume that the maximum kinetic energy obtained by the cup is 2.6 J and that air resistance is negligible.

b) What happened to the 2.6 J of kinetic energy after the crash?

The energy was converted to sound, kinetic and thermal energy

Homework

Read: Pg. 143Practice Problems: Pg. 143 #7-10