Momentum, please help!

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I'm doing AQA double science, in my 2nd year and I really don't understand Momentum, can anybody help me please? :)

Posted: 02-03-11 19:21 by Ruby R

Momentum is just the product of a body's Mass and velocity. Therefore Momentum = mass x Velocity. Momentum is measured in Kgm/s. kg being the unit of mass and m/s the unit of velocity. The principle of conservation of momentum states that 'momentum before = momentum after.' So you can use that fact to work out the initial velocity or final velocity of either of the objects involved in a collision.

Say there was one car of mass 70kg travelling at 10m/s that hit a stationary car of mass 60kg from behind. then the total momentum before the collision was - (70x10) + (60x0) its zero because the car was stationary. The final mass is 70 + 60 because they would be moving as one body. So 130kg. And because the initial momentum has to equal the final momentum then 700 = 130 x velocity. therefore velocity = 700/130 = 5.38 m/s

Dont know how much help that will be :)

Posted: 06-03-11 16:57 by Sam

Also just to add, I was asked in my AQA science exam what momentum had and basically:

 Momentum is a vector quantity with a size and a directon :)

Posted: 07-03-11 22:12 by Anthony Gifford

Sam when you're working out the mass of the car and you have (70x10) + (60x0) becuase it is zero becuase the car is stationary, then why isnt 60x0 not equal 0? :)

Posted: 31-03-11 09:55 by Sally Richards

Sam is right, sally read it again slowly.

"The final mass is 70 + 60 because they would be moving as one body."

Posted: 25-04-11 10:32 by alex mackenzie

yes, what sally said :D

oh and if your doing higher tier, you will also need to know that:

force = change in momentum / time taken

this is the theory behind crumple zones, airbags and seat belts and that - it's so that when a collision happens, the longer the time taken for the body's momentum to reach zero then the lower the force impact on the body. that's why seat belts are designed to stretch a bit in a collision - ever notice when a car stops suddenly, your seat belt moves with you for a bit then locks you in, this is so it increases the time, therefore lowering the force impact, so you experience a lower force.

dunno if you are doing higher tier, but you need to know this theory about momentum as well as momentum = mass x velocity if you are taking the higher paper exam..........

Posted: 26-04-11 18:31 by Aimee

im actually really smart but this girl called emily really pulls me down so much. shes really ugly and fat, but dont tell her.

Posted: 27-04-11 11:15 by emily


Posted: 27-04-11 11:34 by SARAH

Thank you everyone!

Posted: 27-04-11 14:46 by Ruby R