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Help with mechanics

A ball at rest of dropped at height h m onto a horizontal surface. After striking the surface it rebounds to half its original height. Show that the time
t taken from the instance the ball is dropped to the instant it strikes the floor for the second time is given by t=(2+sqrt2)(sqrt (h/g)).
Where g is the acceleration due to gravity
Reply 1
Original post by Kffh
A ball at rest of dropped at height h m onto a horizontal surface. After striking the surface it rebounds to half its original height. Show that the time
t taken from the instance the ball is dropped to the instant it strikes the floor for the second time is given by t=(2+sqrt2)(sqrt (h/g)).
Where g is the acceleration due to gravity

Should be a relatively straightforward application of suvat? What are you stuck with?
Reply 2
Original post by mqb2766
Should be a relatively straightforward application of suvat? What are you stuck with?

I just thought we don’t have all the necessary info for suvat. S=h, u=0 is all I got
Reply 3
Original post by Kffh
I just thought we don’t have all the necessary info for suvat. S=h, u=0 is all I got

You can find the time to hit the ground in terms of h and g?
Thats the first part.
Reply 4
Original post by mqb2766
You can find the time to hit the ground in terms of h and g?
Thats the first part.

How?
Reply 5
Original post by Kffh
How?

What suvat relates u, a, t, s?
Reply 6
Original post by mqb2766
What suvat relates u, a, t,S

image.jpgWould it be something like this? I’m having trouble making t the subject
Reply 7
Original post by Kffh
image.jpgWould it be something like this? I’m having trouble making t the subject

why u=30? The ball is at rest initially.
Reply 8
Original post by mqb2766
why u=30? The ball is at rest initially.

Sorry, I’m getting confused between questions
Reply 9
Original post by Kffh
Sorry, I’m getting confused between questions

image.jpgThis?
Original post by Kffh
image.jpgThis?

Thats the first part of the answer. Now find the time to travel up to and back from half the height, which is the bounce phase.
Original post by Kffh
What will u be then bcs it won’t be zero?

Are you talking about the upwards or diwnwards phase of the bounce?
Reply 12
Original post by mqb2766
Are you talking about the upwards or diwnwards phase of the bounce?

image.jpgI did this for the whole thing from the initial drop to the second time it strikes the ground
Original post by Kffh
image.jpgI did this for the whole thing from the initial drop to the second time it strikes the ground

The rebound complicates things? You can't do a single calculation.
Reply 14
Original post by mqb2766
The rebound complicates things? You can't do a single calculation.

What values am I using for the rebound. I know h and g, but what is the third one?
Original post by Kffh
What values am I using for the rebound. I know h and g, but what is the third one?

You could use those to work out u. You know that v=0 when s=h/2.
A smarter way is to exploit the symmetry and consider the downwards phase after the bounce.
Have a go at both?
What paper is that from

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