Hi, I can\'t figure out the normal force part of this question, please help! A 0
ID: 1290876 • Letter: H
Question
Hi, I can't figure out the normal force part of this question, please help!
A 0.097 kg remote control 15.7 cm long rests on a table, as shown in the figure below, with a length L overhanging its edge. To operate the power button on this remote requires a force of 0.320 N. Assume the mass of the remote is distributed uniformly, and that the power button is on the end of the remote overhanging the table.
How far can the remote control extend beyond the edge of the table and still not tip over when you press the power button?
5.87 cm
How large is the normal force when the button is pressed?
_______ N
Explanation / Answer
This question is solved by equation the momentum of the weight (which acts at the centre of mass = 15.7/2) and the force on the button. Let the overhanging length be L.
Next it also says when the button is pressed the remote does not get tipped of. So let us find what happens when the remote just gets tipped off. As the remote gets tipped off it looses its contact with the surface, so the normal force at that point becomes zero.
Now according to the given condition lets see if by putting L as 5.87 cm we are able to balance the moment about the edge.
(15.7/200 - L) x 0.097 x 9.81 (acceleration due to gravity) = 0.320 x L
Putting L = 0.058,
LHS = 0.0198 x 0.097 x 9.81 = 0.0188411
RHS = 0.320 x 0.0587 = 0.018784
So, LHS = RHS, i.e. it is the condition of just balancing. So the normal force in this case will be zero
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