Kinetic Energy

Key Vocabulary

Energy

The capacity to do work or the ability to cause change in a physical system.

Kinetic Energy

The energy an object possesses due to its motion, dependent on its mass and speed.

Joule

The standard international (SI) unit of measurement for energy and work, abbreviated as J.

Work

The measure of energy transfer that occurs when an object is moved by an external force.

Scalar

A physical quantity that is fully described by its magnitude or numerical value alone.

What is Kinetic Energy?

• Kinetic energy is the energy an object has because of its motion.

• It depends on the object's mass and its velocity, or speed.

• More mass or velocity means the object has more kinetic energy.

• An object at rest has zero kinetic energy since it is not moving.

Solved Example 1
A 6 kg bowling ball is rolling down the lane at a speed of 7 m/s. What is the kinetic energy of the bowling ball?

Step 1: Analyze and Sketch the Problem

Solved Example 1
A 6 kg bowling ball is rolling down the lane at a speed of 7 m/s. What is the kinetic energy of the bowling ball?

Step 2: Solve for the Unknown

Solved Example 1
A 6 kg bowling ball is rolling down the lane at a speed of 7 m/s. What is the kinetic energy of the bowling ball?

Step 3: Evaluate the Answer

• The calculation is done correctly. Squaring the velocity first is important.

• The final unit is Joules, which is correct for energy. The answer is positive, which is expected for kinetic energy.

Calculating Kinetic Energy

What is the Work-Energy Theorem?

Solved Example 3
A 1,500 kg car accelerates from 10 m/s to 25 m/s. Calculate the work done on the car during this acceleration.

Step 1: Analyze and Sketch the Problem

Solved Example 3
A 1,500 kg car accelerates from 10 m/s to 25 m/s. Calculate the work done on the car during this acceleration.

Step 2: Solve for the Unknown

Solved Example 3
A 1,500 kg car accelerates from 10 m/s to 25 m/s. Calculate the work done on the car during this acceleration.

Step 3: Evaluate the Answer

• The car sped up, so its kinetic energy increased, which means positive work was done on it. Our answer, 393,750 J, is a positive value, which is consistent.

• The unit for work and energy is Joules (J), which is correctly used in the answer.