## Physics: Principles with Applications (7th Edition)

a. 90 $\frac{kg \cdot m}{s}$ b. 11000N
a. The impulse given to the nail is the opposite of the hammer’s change in momentum. Let the positive direction be the direction of the hammer’s motion. $$-\Delta p_{hammer} = -m \Delta v = -(12 kg)(0-7.5 \frac{m}{s}) = 90 \frac{kg \cdot m}{s}$$ b. Find the average force by dividing the impulse by the time the objects are in contact. $$F_{av}=\frac{\Delta p}{\Delta t}=\frac{90 kg \cdot m/s}{8.0 \times 10^{-3} s}\approx 11000 N$$