Problem 68GP

A sled slides without friction down a small, ice-covered hill. If the sled starts from rest at the top of the hill, its speed at the bottom is 7.50 m/s. (a) On a second run, the sled starts with a speed of 1.50 m/s at the top. When it reaches the bottom of the hill, is its speed 9.00 m/s, more than 9.00 m/s, or less than 9.00 m/s? Explain. (b) Find the speed of the sled at the bottom of the hill after the second run.

Solution 68GP:

Step 1 of 2

Let the initial height was h.

The sled started from rest with zero initial velocity.

Finally it reached the bottom with a final speed of 7.50 m/s.

By the conservation of mechanical energy,

.