1. A block is given a push so that it slides up a ramp. After the block reaches its highest point,..

1. A block is given a push so that it
slides up a ramp. After the block reaches its highest point, it slides back
down, but the magnitude of its acceleration is less on the descent than on the
ascent. Why?

2. Cross-country skiers prefer their skis
to have a large coefficient of static friction but a small coefficient of
kinetic friction. Explain why. [Hint: Think of uphill and downhill.]