[As_Dust_Dances_]

I'm not sure if there's already a thread yet but here's a new one anyway Feel free to post questions and I'll try to answer them. Anyone else finding time graphs annoying?

[Soggy Cherry]

Hey! Just had a go at the Jan 2012 paper, which I hadn't already done, and there was a question on collisions. Usually I find these ones the easiest on the paper but I couldn't figure this one out and there isn't a detailed mark scheme which has been released yet. Basically: P and Q moving in same direction, P has mass 0.3 and is travelling at 2.2, Q has mass 0.5 and is travelling at 0.8. They collide (obviously) and afterwards 'the speed of P is reduced by 50% and its direction of motion is unchanged'. Find the speed of Q afterwards. Couldn't figure out the right answer, which by the way is apparently 1.46m/s

[As_Dust_Dances_]

(Original post by Soggy Cherry)
Hey! Just had a go at the Jan 2012 paper, which I hadn't already done, and there was a question on collisions. Usually I find these ones the easiest on the paper but I couldn't figure this one out and there isn't a detailed mark scheme which has been released yet. Basically: P and Q moving in same direction, P has mass 0.3 and is travelling at 2.2, Q has mass 0.5 and is travelling at 0.8. They collide (obviously) and afterwards 'the speed of P is reduced by 50% and its direction of motion is unchanged'. Find the speed of Q afterwards. Couldn't figure out the right answer, which by the way is apparently 1.46m/s

momentum before = momentum after so you should get:

(0.3 x 2.2) + (0.5x0.8) = (0.3x1.1) + 0.5v (1.1 comes from half of 2.2)

0.66 + 0.4 = 0.33 + 0.5v

so 0.5v = 0.73

so v= 0.73/0.5 => 1.46ms^-1

Hope that helps I haven't done the Jan12 paper yet so it's also practice for me too!

[Soggy Cherry]

(Original post by As_Dust_Dances_)
momentum before = momentum after so you should get:

(0.3 x 2.2) + (0.5x0.8) = (0.3x1.1) + 0.5v (1.1 comes from half of 2.2)

0.66 + 0.4 = 0.33 + 0.5v

so 0.5v = 0.73

so v= 0.73/0.5 => 1.46ms^-1

Hope that helps I haven't done the Jan12 paper yet so it's also practice for me too!

I feel like such an idiot! Did all that but instead of multiplying 1.1 and 0.3, I added them haha, and couldn't even spot it myself! But thanks a lot though Should have a go at it if you could find it then! Though I had to get it from my teacher because I don't think it's allowed to be online yet? As for time graphs, I just struggle finding the displacement when it's a shape I've forgotten how to find the area of, which is my fault and can easily be fixed