1996 past paper and holiday revision

[Connor Einstein]

I dont get on paper 1- 26,27 or 18

[Suzy]

For the 1996 Paper II I've done this question like 5 times and it's driving me crazy - can someone help???!

3a. i) Calculate the speed of the cars immediately after the collision.

so I done; m1 = 1200kg m2 = 1000kg m1u1 + m2u2 = m1v1 + m2v2
u1 = 18.0m/s u2 = -10.8m/s (1200 x 18) + (1000 x -10. = 1200v + 1000v
v1 = ? m/s v2 = ? m/s 10800 = 2200v
v = 4.909 m/s (4sigfigs)


ii) But then you have to show its inelastic and I keep getting Ek before to be less than Ek after which isnt possible!!! is it???

Please help

[Connor Einstein]

From what i gather i thought it was this:

Ek before = (0.5*1200*18<2>)+(0.5*1000*-10.8<2>)
Ek= 136080J

speed after collision:

m1=1200
u1=18
m2=1000

m1u1=(m1+m2)v1
1200*8=(1200+1000)v
21600/2200=v
9.82=v


Ek after:

Ek= (0.5*1200*9.82<2>)+(0.5*1000*9.82<2>)
Ek= 106075.64 J


Im not 100% so open to feedback

[S.McGrath]

emm for 3a)i) i got 4.9ms^-1

M1U1+M2U2=V1(M1+M2)
1000x (-10. + 1200x18=V1 (1200+1000)
-10800+21600 = 2200V1
10800=2200V1
V1=4.9ms^-1


ii) i got ek before= 1/2xM1xU1^2+1/2xM2xU2^2
=0.5x (-10.^2x1000+0.5x1200x18^2
=58320+194400
=252720J

EK after=1/2xM1xV1^2+1/2xM2xV2^2
=0.5x1000x4.9^2 + 0.5 x 1200 x 4.9^2
=12005+14406
=26411J

there is a decrease in Ek before because it reduces from 252720J to 26411J, therefore it is inelastic


im pretty confident but farrell will probably burst my bubble

[S.McGrath]

ps they wee smilies are really the number 8 with a bracket bside it

[Admin]

First up it is good to see you using this to share ideas, excellent.
If the cars collide and come together then the final speed is 4.9 m/s well done Suzy and Steven. The Ek will decrease as proved by Mr. McGrath, take a a bow no bubble to burst

[Connor Einstein]

ohhhh i can see what i done wrong

[S.McGrath]

u kiddin sir :O i actually got it right :O,
i seen connor and suzy struggling i thought i must have done something wrong !!!!!!!!!!!

[Suzy]

Lol thank you but Mr Allan bet yous all to it lol
I'd done axctly the same as stephen but when you finished with 252720J and 26411J well I miscounted the numbers and for some reason thought that 26411 > 252720........i know its embarassing

Took me and Mr Allan like 15minutes to figure it out as well

[S.McGrath]

mr allen

legend