Dekoyl's Questions

[Over9000]

btw, wats the answer to the second question, I have 7.3m, not sure if its right?? (ill post my working if it is)

[dekoyl]

btw, wats the answer to the second question, I have 7.3m, not sure if its right?? (ill post my working if it is)

The answer is 2.87m.

[Over9000]

oh, kk, way off, ill have to check where I made an error 

[Over9000]

Ok, I shall try to explain what the picture is like
Inclined plane to horizontal, Imagine a block halfway (doesnt have to be) along the incline plane and a pulley (simple one pulley) at the very top of the plane, now, the rope connects to the block which is on the inclined plane goes over the single pulley and then downwards connected to another lighter block. So you can imagine a block on an inclined plane, connected to a block which is hanging freely in mid air via the pulley system (I dont know if you will understand this, a bit hard to explain).

So (block on inclined plane) = (block hanging freely)
     
     
     
     
     
     
     
     use constant acceleration forumla
     
     

If you still cant picture it (which may make the working out seem hard to comprehend), send me a pm and ill scan my working out of the question by hand.

[dekoyl]

No it's okay Your explanation was great so I got it.
Thanks heaps again Over9000 =]

[dekoyl]

Momentum: A heavy truck collides head on with a car one fifth its mass. The car and truck were both travelling at 20 above the speed limit. During the collision, what is the ratio? Answer: 1


Thanks!

[dcc]

Momentum: A heavy truck collides head on with a car one fifth its mass. The car and truck were both travelling at 20 above the speed limit. During the collision, what is the ratio? Answer: 1

What is the ratio?  Which ratio?

[dekoyl]

What is the ratio?  Which ratio?

That's the exact question. =(
It's meant to be in relation to momentum and impulse. And the exact answer is 1. (Ratio of 1:1?)

[TrueTears]

Momentum: A heavy truck collides head on with a car one fifth its mass. The car and truck were both travelling at 20 above the speed limit. During the collision, what is the ratio? Answer: 1

What is the ratio?  Which ratio?

yeah, what ratio does it ask? ratio of the speed? or...?

[dekoyl]

yeah, what ratio does it ask? ratio of the speed? or...?

This is from page 11 of "Motion question booklet.doc" in the thread you created with motion notes + practice SACs.
I'm not sure; This is the exact question (copy + paste):

20. A heavy truck collides head on with a car one fifth of its mass. The car and the truck were both travelling at 20 kmh-1 above the speed limit.
During the collision what is the ratio     ?

Ans: 20) 1

Yeah looks like there might be something missing judging from the space between 'ratio' and '?'.

Thanks anyway dcc and TT

[TrueTears]

hmm yeah, might be a faulty question lol

[dekoyl]

A simple one:

A rubber ball bounces from a height of 1.0m onto a wooden table and rebounds to a height 0.8m.
Explain how the momentum is conserved during the collision between the ball and the table.
Worth 2 marks and I didn't get any marks.

[TrueTears]

Momentum is always conserved, here the ball does not rebound to its original height because some momentum is transferred into the table.

Considered the table as a car and the ball as a much lighter car.

The table car is stationary, where as the ball car crashes head on into the table car.

Assuming they both rebound, the table car rebounds a tiny bit (most likely none here cos the ball is so light) and the ball car bounces back in the direction where it came from, but it's lost some speed (because its transferred some momentum into the table car) and so it does not go back fully where it started.

[dekoyl]

Thanks TT - I guess my explanation wasn't good enough But your explanation should please my marker.

[Flaming_Arrow]

Momentum is always conserved, here the ball does not rebound to its original height because some momentum is transferred into the table.

Considered the table as a car and the ball as a much lighter car.

The table car is stationary, where as the ball car crashes head on into the table car.

Assuming they both rebound, the table car rebounds a tiny bit (most likely none here cos the ball is so light) and the ball car bounces back in the direction where it came from, but it's lost some speed (because its transferred some momentum into the table car) and so it does not go back fully where it started.

And the Normal Reaction Force> Weight, otherwise it wouldn't bounce.