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Question
I am having trouble understanding this. For example:
The coefficient of sliding friction for steel on ice is .050, what force is required to keep a man weighing 150 lbs moving at a constant speed? what about a man with a mass of 62 k6?
Where do I start?? What formula should I use??
Also: I am in the 11th grade and this is my first physics class.
Hi Andrew,
I am sorry for the delay in my answer, I took a short vacation :-).
You start with Newton's laws which tell you that to keep an object at rest or (this is the important bit) in motion at a constant velocity, the TOTAL force acting on it must be zero. So, your external force must compensate for the friction force, which slows the man down. It must have the same magnitude and opposite orientation.
The magnitude of the friction force is F_frict = f*m*g, where f is the coefficient of friction 0.050, m is the man's mass 62 kg, and g is gravitational acceleration on the Earth's surface 9.81 m/s^2. The result is about 30N, that's the answer and there is no magic in it.
Cheers,
Daniel
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Daniel Mazur
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