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Define the moment of a couple

The moment of a couple is the force times the perpendicular distance between the lines of action of the force.

Answered by Heather W. • Physics tutor

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An object with weight w is suspended from two strings at angles θ1 and θ2 to the vertical and with tensions T1 and T2. How would you resolve the vertical and horizontal forces?

Horizontal: T1 sin θ1 = T2 sin θ2Vertical: T1 cos θ1 + T2 cos θ2 = w

Answered by Heather W. • Physics tutor

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If a wire loop moves at constant speed into a region where there is a magnetic field, why is a current induced in the wire?

In this question, a square wire loop of length L and resistance R starts in a region with no magnetic field, and moves at a speed v into a region with magnetic field B, which is acting perpendicular to th...

Answered by Gus B. • Physics tutor

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From what height, h, should a rail-cart fall to complete a loop-the-loop of radius r without falling off a the track? Assume the track on which the rail-cart travels is smooth and express h in terms of r.

This question combines the principles of energy conservation and circular motion. The insight is to realise the condition for which the rail-cart will fall off of the track - when there is no contact forc...

Answered by Benjamin R. • Physics tutor

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A box initially at rest is on a plank, of length 5m, that is elevated at an angle such that tan(a)=3/4. When it reaches the end of the plank it has velocity 5ms^-1. Calculate the average frictional force on the box.

In physics questions it is useful to not plug numbers in until the end and instead work through algebraically. Let's say the angle of elevation is a, the mass is m, the velocity at the end of the plank is...

Answered by • Physics tutor

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