What amount of force must be applied to 6kg block moving at 13m/s to slow down to 5m/s in a distance of 4.5m?The Friction between them is 75N?

Expert Answers
jeew-m eNotes educator| Certified Educator

We can do this using Newtons second law of motion.

To stop the moving block we have to apply a force against its motion. Both friction and the applied force result in decrease the velocity of the block.


Using equations of motion

`V^2 = U^2+2aS`

`a = (V^2-U^2)/(2S)`

`a = (5^2-13^2)/(2xx4.5)`

`a = -16m/s^2`


Acceleration is negative because we have a deceleration.


Let us say the force is P at the opposite direction to the movement.

Using F = ma to the direction of motion

`-P-75 = 6xx(-16)`

      `P = 21N`


So the required external force is 21N at the direction opposite to the movement of block.