Question

An object starts from rest at x=0 m and moves with a constant acceleration of 1.6 m/s^2 along the x-axis during its journey from x=12.8 m to 20.0 m its average velocity will be?

Answer 1

Initial velocity = u = 0 m/s

Constant acceleration = a = 1.6 m/s^2

Final velocity and displacement equation is given by  

V^2 – u^2 = 2as.

For s = 12.8m, the final velocity is

V^2 – 0 = 2*1.6*12.8

V = √(40.96) = 6.4 m/s

For s = 20m, the final velocity is  

V^2 – 0 = 2*1.6*20 = 64  

V = √(64) = 8 m/s

Velocities at 12.8m and 20m are 6.4m/s ad 8m/s.

Since the acceleration is constant, the speed increase at every second is constant.  

That means average of all the numbers is same as average of first and last.  

Hence average velocity = (6.4+8)/2 = 7.2m/s.