Question

Physics Homework:

1) A 1400 kg car goes around the corner at a constant speed of 15.0 m/s. If the centripetal acceleration is 5.00 meters per second per second, what is the radius of the corner?

2) A 75 kg box is pushed across a level floor. If the force required to maintain constant velocity is 255 N, what is the coefficient of kinetic friction?

Answer 1

(1)

Centripetal force required to move an object of mass m in a circular motion of radius r at constant speed v is

By Newton's second law F=ma

(2)

There are four forces acting on the box: mg is the gravitational force of the Earth, N is the normal force by the floor, F_r is the force of kinetic friction, F_push is the pushing force. The free-body diagram of the box is shown below:

The box is not allowed to move in the vertical direction, the net force on the box in this direction is zero

The force of kinetic friction on the box is

The net horizontal force on the box is

Given the box moves at constant velocity, the acceleration of the box is zero, so the net force on the box is also zero