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How do you find the acceleration of an object when the only forces are weight and the force of the ground?
Biomechanical research has shown that when a 67 kg person is running, the force exerted on each foot as it strikes the ground can be as great as 2300 N.
If the only forces acting on the person are (i) the force exerted by the ground and (ii) the person's weight, what are the magnitude of the person's acceleration?
2 Answers
- Anonymous1 decade agoFavorite Answer
This is a little bit of a trick question. You know that for every force there is an equal and opposite force, so the force each foot is exerting on th eground is 2300 N. So the acceleration must be F = ma >>>
a = F/m = 2300 / 67.
The tricky bit is that this acceleration is at some angle to the horizontal, and that a lot of that energy is spent lifting the legs and body of the runner, and not in forward propulsion, so you really have no idea of what is happening to the runner, taken as a whole.
- Anonymous5 years ago
I'm not sure of the complete answer, but this might help. What you have to do is to calculate the speed of the object when it hits the ground in order to multiply that speed by the weight of the object. (You also have stated "ft" in one place and "m" in another (?)) The formula for computing gravitational acceleration in a vacuum is 32 ft. per second per second. I have never heard the term "instantaneous velocity", and it may not be relevant here. Hope this helps.