A 5 kilogram stone is dropped on a nail and drives the nail 0.025 meter into a piece of wood. If stone is moving at 10 meters per second when it hits the nail, the average force exerted on the nail by the stone while the nail is going into the wood is most nearly

A. 10 N

B. 100 N

C. 1000 N

D. 10,000 N

E. 100,000 N

**(GR8677 #8)**

**Solution:**

Force: F = ma

The acceleration when the stone hits the nail:

2ay = v² + v

_{0}²

v

_{0}= 0

→ a = v²/2y = 10²/2(0.025) = 2 × 10³ m/s²

→ F = 5 × 2 × 10³ = 10,000 N

**Answer:**D