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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
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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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Define a "Vector Quantity" and list 2 examples.

a) A vector quantity is a quantity with both magnitude and direction. (opposite would be a "scalar quantity") b) examples could include acceleration, weight, displacement, velocity etc.
TF
Answered by Thomas F. • Physics tutor
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If the force between two point charges of charge 'Q1' and 'Q2' which are a distance 'r' apart is 'F' then what would the force be if the charge of 'Q1' is tripled and the distance between them doubled?

We know from Coulombs law that the force between two point charges is directly proportional to the product of the magnitudes of each charge and inversley proportional to the square of the distance between th...
JH
Answered by Joseph H. • Physics tutor
8365 Views

A gun of mass 10kg fires a bullet of mass 240g at a speed of 300ms-1. What is the speed of the gun's recoil?

First, convert the mass of the bullet into SI units -> 240g=0.24kg The law of the conservation of momentum states that m 1 v 1 =m 2 v 2 . To find the speed of the gun, rearrange for v 1 to give v 1 =m 2 v...
JF
Answered by Jonny F. • Physics tutor
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