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Describe, using a diagram, the forces acting on the system of an object tethered to a string, rotating around a fixed point in free space. Will the string ever become horizontal?

Firstly, I would start by drawing a diagram of the system on the whiteboard, showing the object attached to the string, and the string at a fixed point. I would show using arrows that the object was rotat...

Answered by Simon S. • Physics tutor

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There is a point between the Moon and the Earth where the gravitational attractions are equal and opposite. How much further is this point from the Earth than the Moon

Using the formula for gravitational attraction between the Moon/Earth and a test mass, m. We determine F_E = (G*M_Em)/(r_E² ), F_M= (GM_M<...

Answered by Paul D. • Physics tutor

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A rocket travels with constant velocity in a straight line in deep space. A ball is thrown from the back to the front (ie from the thrusters to the nose). Describe the path of the ball. Describe the path if the rocket were accelerating along this line.

Consider first what happens when the rocket travels with constant velocity. Constant velocity implies that there are balanced forces (or indeed no forces) acting on the rocket. This is Newtons 1st Law. We...

Answered by Sam W. • Physics tutor

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Derive an expression for the time taken, (t) for a test mass to fall to the ground from a height (h) in a uniform gravitational field (g = 9.81 ms^-2)

We first build an intuition for exactly what acceleration is and what we expect to happen. In the uniform gravitational field approximation, we assume h to be much less than the radius of the Earth. There...

Answered by Charlie B. • Physics tutor

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When a 470 micro farad capacitor is discharged through a fixed resistor R, the pd across it decreases by 80% in 45 s. Calculate the time constant of the circuit

Using the equation V=V₀e^-t/RC where RC is the time constant to be calculated: We know that the pd decreases by 80%, therefore the pd remaining, V is 0.2*V₀. Putting this i...

Answered by Peter K. • Physics tutor

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