A hammer

A hammer weighing 500 g hits the nail at a speed of 3 m/s. What is the average force acting on the nail, which penetrates the board to a depth of 5 cm?

Correct answer:

F =  45 N

Step-by-step explanation:

$$\begin{gathered} m=500\text{g}\to \text{kg}=500:1000\text{kg}=0.5\text{kg} \\ v=3\text{m/s} \\ s=5\text{cm}\to \text{m}=5:100\text{m}=0.05\text{m} \\ E=\frac{1}{2}\cdot m\cdot v^2=\frac{1}{2}\cdot 0.5\cdot 3^2=\frac{9}{4}=2.25\text{J} \\ E=W=Fs \\ F=E/s=2.25/0.05=45\text{N} \end{gathered}$$

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