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State Lenz's law and hence describe and explain what happens to a magnet travelling through a metal tube

Lenz's law states that the direction of current due to emf induced by a changing magnetic flux is always such that it opposes the change that induced it. When a magnet travels through a copper tube this indu...
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Answered by Melisande C. • Physics tutor
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What is resonance

Resonance is the effect of an external driving force which causes a system to ocsillate with a greater amplitude at certain frequencies. All objects have a natural frequency, and this specific property deter...
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Answered by Michalis C. • Physics tutor
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A body is moving at 70km/h and has a mass of 130kg, calculate its maximum kinetic energy.

Firstly, the speed is not given in SI units, this is modified by changing the units from km/h to m/s by the following relationship; 70km/h = (70000/3600)m/s. Once this is complete the equation for kinetic en...
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Answered by Joe I. • Physics tutor
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A ball is launched from ground level at 5m/s at an angle of 30 degrees above the horizontal. What is its height above ground level at the highest point in its trajectory?

STEP 1: Draw a diagram! Remember to include all the useful information you are given in the question i.e. the initial velocity of the ball (5m/s at 30 degrees above the horizontal). This can be shown as a ve...
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Answered by Iestyn H. • Physics tutor
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A block of mass (m) is placed on a rough slope inclined at an angle (a) to the horizontal, find an expression in terms of (a) for the smallest coefficient of friction (x), such that the block does not fall down the slope.

The first thing to do as with any mechanics question is draw a force diagram with the weight (mg), the friction (F) and the normal reaction (R). As we are finding the smallest coefficient of friction possibl...
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Answered by Ollie W. • Physics tutor
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