PHYS - Calculating Moments of Force
Physics, moment, force - IBDP | DSE | GCE | IAl | AP Physics
For IGCSE Physics, the equation that you should know about moment is:
moment = force x distance from pivot
The diagram shows the side view of a laptop computer. A student opens the computer with an upward force of 4.2N. The force is applied 0.25m from the pivot.
(a) Calculate the moment of the force that opens the computer.
moment = force x distance = 4.2 x 0.25 = 1.05 N·m
(b) The student finds that 4.2N is the minimum upward force needed to open the computer. Then the student applies a downward force, F, to close the computer. Explain why the minimum force needed to close the computer is likely to be less than 4.2N.
The moment of weight of the laptop acts in the same direction as the force to close the computer. Therefore, it takes less force to close the laptop than to open it.
A student investigates the principle of moments. He connects a ruler to a stand with a pivot. He hangs a 2N weight from the 60cm mark on the ruler. He uses a forcemeter to hold the ruler horizontal.
(a) How can the student check that the ruler is horizontal?
(b) Calculate the moment of the 2N weight.
moment = 2 x 0.6 = 1.2 N·m
(c) The student holds the ruler horizontal with the forcemeter at the 10cm mark. He expects the reading on the forcemeter to be 12N. Is the student correct?
Two fishermen uses a pole to carry some fish. Fisherman A and B feel different forces on their shoulders. Explain which fisherman feels the larger force.
A student can use a claw hammer to pull a nail from a piece of wood. The diagram shows two forces acting on the hammer. Suggest three ways that the student can increase the moment on the hammer.
The force that causes the moment which makes it possible to pull the nail from the wood is F1.
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