Question

A girl on a skateboard (total mass of 40 kg) is moving at a speed of 10 m/s at the bottom of a long road. The road is inclined at 20° with respect to the horizontal. If she travels 14.2 m upward along the road before stopping, without pushing in any way, what is the net frictional force on her?

(a) 274.08 N
(b) 3891.52 N
(c) 1945.76 N
(d) 0 N

Answer 1

The net frictional force on the girl on the skateboard is 3891.52 N.

Step-by-step explanation:

To find the net frictional force on the girl, we need to calculate the work done by gravity and compare it to the work done by the normal force. The work done by gravity is given by the equation:

W = m * g * d * cos(theta)

Where:
m = mass (40 kg)
g = acceleration due to gravity (9.8 m/s^2)
d = displacement upward along the ramp (14.2 m)
theta = angle of the ramp (20 degrees)

The work done by the normal force is zero, as it acts perpendicular to the displacement. Therefore, the net frictional force on the girl is equal to the work done by gravity:

Net frictional force = m * g * d * cos(theta)

Substituting the given values, we get:

Net frictional force = 40 kg * 9.8 m/s^2 * 14.2 m * cos(20 degrees)

Simplifying this expression gives us:

Net frictional force = 3891.52 N