GS-1 Physical Sciences Question 33

[ozairmh8911]

How can the car be exerting a force of 300 N? Relative to what?

[jellywing_2058]

For the question “how the car be exerting a force of 300 N? Relative to what?” we have to understand the nature of friction. Friction is caused due to molecular irregularities on the two surfaces in contact. Due to it the actual contact area is extremely small and the pressure at these points is large enough to cause the two points to weld; we call it a cold weld. To be able to move the body we need to break these cold welds. The force of the car of 300 N is certainly not able to do so and the car does not move.

The force that does break them and enables relative motion is called the limiting force of static friction and an empirically/ experimentally found relation for it is:

Fs = µs x N

where:
µs = Coefficient of Static Friction – depends on the nature of the two surfaces in contact

N = Normal Reaction