Kinematics: Acceleration

 

 

Acceleration is the rate-of-change of velocity.

 

 

Average Acceleration () is the ratio of the change in its velocity over the time elapsed in the process.

 

 

 

 

 

 

 

Whenever an object speeds up or slows down, its velocity changes size and it has an acceleration along, or tangent to, the path traveled. Whenever an object moves in a curve its velocity changes direction and it has an acceleration perpendicular to the path traveled.

 

Example 1

A car accelerates along a straight road from rest to 75 km/hr in 5.0 s. What is the magnitude of its average acceleration?

 

 

 

 

Example 2

(a) If the velocity of an object is zero, does it mean that the acceleration is zero?

(b) If the acceleration is zero, does it mean that the velocity is zero?

Think of some examples.

 

Example 3

An automobile is moving to the right along a straight highway, which we choose to be the positive x axis, and the driver puts on the brakes. If the initial velocity is and it takes 5.0 s to slow down to , what was the car's average acceleration?

 

 

 

 

 

Instantaneous Acceleration:

 

 

The slope of the tangent to the velocity-time curve at any moment is the instantaneous acceleration at that moment.

 

 

Uniformly Accelerated Motion

Constant Acceleration

Now solve for the final velocity.

This is the first Kinematics equation.

 

 

 

 

 

 

 

Part 2