Using the laws of conservation of energy it is possible to calculate the combined velocity of two astronauts colliding in space...
...in case that was on your bucket list :)
You don't need to memorise everything on this page (you will always have enough information to work out the answers from scratch), but taking the time to do so could help you to rule out some Paper 1 multiple choice answers under time pressure.
Key Concepts
An elastic collision is one in which Ek and momentum are conserved.
In a collision between two equal masses in 1D the velocities simply swap.
When a body explodes, energy is given to the parts so Ek is obviously not conserved. However, momentum is conserved.
Use quizzes to practise application of theory.
START QUIZ!
A large rock is attracted to the Earth as shown.
As the rock is travelling towards the Earth which of the following quantities are conserved?
PE changes to KE
Momentum is always conserved if bodies are isolated
A rock orbits the earth at constant speed.
Considering the earth and rock to be isolated from the rest of the universe which of the following are constant?
No work is being done so energy is constant
Bodies isolated so momentum is conserved (The Earth also has a small momentum)
Change of direction makes velocity change.
Observe the collision between two identical balls
Which of the following are conserved
Angle is not 90° so not elastic
Two balls explode from one another as shown (reason for explosion unknown)
If the KE of the red ball is 20 J
The KE of the blue ball = J
KE of red ball = 1/2 m 42 = 8m
velocity of blue ball = 1 ms-1
KE of blue ball = 1/2 x 4m x 12 = 2m this is 1/4 of red ball KE
two identical spacemen collide and stick together as shown.
The total KE before the collision was 200 kJ. The amount of KE lost is:
After collision the velocity is 1/2 but mass is 2 x
KE before = 1/2 mv2 KE after = 1/2 x 2m x(v/2)2 = (1/2 mv2)/2
How much of Collisions have you understood?
Twitter 
Facebook 
LinkedIn