# Help with force

1. Dec 3, 2003

### badboyben03

can someone give me the formula needed to do this problem?

"a karate strike hits wooden blocks, the hand undergoes an acceleration of -6500 m/s2. Medical data indicates the mass of the forearm and hand to be about 0.8 kg. What is the force exerted on the hand by the blocks?"

am i supposed to convert kg into something else???

2. Dec 3, 2003

### thermodynamicaldude

Based on Newton's third law, forces come in pairs.

Now remember that Force = mass * accelleration

The force the blocks exert on the hand to stop it = -6500 m/s^2 * .8kg which = -5200 newtons, as force is measured in newtons.

Now, forces come in pairs and are equal and opposite,

thus, the force the hand exerts on the bricks is equal and opposite to the force the brick exerts on the hand. Therefore, it would be 5200 newtons, which is the oppositite, of -5200 newtons.

force hand exerts on bricks = 5200 newtons

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