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Using Newton's law of universal gravitation, show that T^2 is proportional to r^3 (where T is the orbital period of a planet around a star, and r is the distance between them).

Newton's law of gravitation is: F G =(GMm)/(r 2 ).First of all, it's a good idea to draw a diagram of the planet and star, labelling the directions of the centripetal force and and the planet's velocity in p...
JB
Answered by Jake B. • Physics tutor
5182 Views

Using Newton's law of gravitation, derive a suitable formula for the escape velocity of an object at Earth's surface.

Newton's law of gravitation is; F = GMm/(r 2 ) Where G is the Universal Gravitational constant, M is the mass of Earth, m is the mass of the object and r is the radius of Earth (no values are needed for this...
CM
Answered by Charlie M. • Physics tutor
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A small ball of mass 150 g is placed at a height of 20cm above the ground on an incline of 35°. It is released and allowed to roll down the slope; what will be the ball's speed when it reaches the ground? Assume friction and air resistance can be ignored.

This question is best solved using conservation of energy, since it is stated that friction and drag (non-conservative forces) can be ignored.When the ball is released at the top of the slope, its initial sp...
RS
Answered by Rhys S. • Physics tutor
2214 Views

What is the minimum frequency of electromagnetic radiation needed for a photon to ionise an atom of sodium? ( An atom of sodium has an ionisation energy of 5.15 eV.)

First, let's define what the ionisation energy is. The ionisation energy is the minimum amount of energy required to remove an electron from the ground state of an atom. That means, if we give an electron in...
AM
Answered by Angus M. • Physics tutor
14159 Views

A ball is dropped from a 5.0m high window. Assuming air resistance is negligible, calculate the time taken for it to hit the ground.

It is helpful to break down questions and draw a diagram. Here we know we have a ball that is being dropped, so it will initially be stationary. Gravity will cause it to accelerate towards the ground at 9.8 ...
CP
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