Changes In Speed

• Forces can cause objects to move faster or slower. That is, forces can cause either an increase in speed or a decrease in speed.

• An increase in speed is known as acceleration.

• This may involve an object that is initially stationary (not moving) or an object that is already moving.

• Example 1

• If you jump out of a plane, you will fall with increasing speed.

• Example 2

• If you start pedalling harder when riding your bike, your speed will increase.

• A decrease in speed is known as deceleration.

• If the force causing the deceleration continues for long enough, it will cause the object to stop moving.

• Example 1

• If a rolling ball approaches an upwards slope, its speed will decrease.

• Example 2

• If you apply the brakes on your bike, your speed will decrease. If you keep applying your brakes, you will eventually come to a stop.

Forces can cause an increase in speed, known as acceleration, or a decrease in speed, known as deceleration.

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