Work-Energy

Question 1

A person skis down a 20 m long snow slope which makes an angle of 25° with the horizontal.

The total mass of the skier and skis is 50 kg.  There is a constant frictional force of 60 N opposing the skier's motion.  The speed of the skier as he/she descends from the top of the slope is 2,5 m·s^-1

1.1) Calculate the magnitude of the net force parallel to the slope   experienced

        by the person.        

1.2)  Calculate the maximum speed of the skier at the bottom of the 20 m slope

Question 2

A bus, of mass 8000 kg, is at point A and is moving at a speed of 20 ms^-1. As it passes point B, which is 100 m from A, its speed has decreased to 5 ms^-1.

2.1) Calculate the difference in mechanical energy between A and B.

2.2) Calculate the magnitude and direction of the average frictional force.