Year 12s: what will be the first way you research your future options? >>

Projectiles

Question 7a.

it appears my answer is incorrect, and the correct way to do this is to solve for t with the part of the projection that occurred after the ball left the surface, and subtract this from the total time, 1 second.

What I DON'T understand is why my method, solving for t in the section before the ball leaves the rough surface, doesn't work as well. Since it doesn't seem to work, what have I actually found by solving for t in the way I've done it?

https://imgur.com/a/1nTRiVn

(edited 5 years ago)

Reply 1

RDKGames

Study Forum Helper

Original post by Illidan2

Question 7a.

it appears my answer is correct, and the correct way to do this is to solve for t with the part of the projection that occurred after the ball left the surface, and subtract this from the total time, 1 second.

What I DON'T understand is why my method, solving for t in the section before the ball leaves the rough surface, doesn't work as well. Since it doesn't seem to work, what have I actually found by solving for t in the way I've done it?

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Reply 2

Illidan2

Apologies. I've since amended my original post, and you should now be able to view them through imgur.

Original post by RDKGames

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Reply 3

Illidan2

I can see why subtracting the time taken for the ball to fall to the ground after it leaves the rough surface from the total time leaves us with the time on the rough surface, but I don't understand why I can't just solve for the time on the rough surface to begin with, rather than finding the other part and subtracting from the total time. I imagine it has something to do with the rough surface itself and that friction is a consideration, but since I already have the velocity of that part I can't see why I can't just use SUVAT.