Question

An object starts from rest with a constant acceleration of 8 m/s along a straight line what is the average velocity over five seconds

Answer 1

`\bar{v}=20\ m/s`

Step-by-step explanation:

Constant Acceleration Motion

It's a type of motion in which the velocity changes by an equal amount in every equal period of time.

If vo is the initial speed, vf the final speed, and t the time, the acceleration is calculated as follows:

`\displaystyle a=(v_f-v_o)/(t)`

The final speed is calculated by solving the above equation:

`v_f=v_o+at`

The object starts from rest (v0=0) with a constant acceleration of a= 8 m/s^2 during t=5 seconds. Thus the final speed is:

`v_f=0+8 m/s^2\cdot 5\ s`

`v_f=40\ m/s`

The average velocity (speed in this case) is

`\displaystyle \bar{v}=(v_o+v_f)/(2)`

`\displaystyle \bar{v}=(0+40)/(2)`

`\boxed{\bar{v}=20\ m/s}`

Note: The average speed could also be calculated as the distance traveled x by the time. It would lead to identical results.