Acceleration

• When an object is changing its velocity, we say that the object has acceleration

• Acceleration is how fast velocity is changing• To accelerate, one must:

– Speed up– Slow down– AND/OR change direction– Can you give an example of each one of these?

Examples of acceleration

• Applying the brakes in a car

• Going around a curve in a car while on cruise control

• Rolling down a hill

• Swinging a bucket over your head

• Hitting a golf ball off a tee

Average Acceleration Formula

• Average acceleration = change in velocity time required for change

• a = v/t = (vf - vi)/t

∆ = change

vf = final velocity

vi = original (initial) velocity

Remember- acceleration is the rate at which velocity changes, speed is the rate at which distance changes

When acceleration is constant…

1. Velocity increases by the same amount over the same time period

2. And, distance covered per second will always increase

Deceleration is slowing down

Zero acceleration is motion at a constant velocity OR not moving at all

Can use a v-t graph to show acceleration– + slope = +acceleration (speed up)– - slope = - acceleration (slow down)– 0 slope = no acceleration