The Student Room Group

M2 Coefficient of Restitution Question

Can someone explain question 6iii)a and b. The solution given was 1.6e^2 and 1.6e^3 respectively, but I have no idea at all as to where these came from...
image.jpg
Reply 1
Original post by Mathematicus65
Can someone explain question 6iii)a and b. The solution given was 1.6e^2 and 1.6e^3 respectively, but I have no idea at all as to where these came from...
image.jpg


The time between the first bounce and second is 1.6e1.6e

The time between the second bounce and third bounce is the time between the first bounce and second bounce decreased by a factor of ee.

So the time between the second and third is 1.6e×e1.6e \times e.

The time between the third and fourth is the time between the second and third decreased by a factor of ee.

So the time between the third and fourth is (1.6e×e)×e(1.6e \times e) \times e.
Original post by Zacken
The time between the first bounce and second is 1.6e1.6e

The time between the second bounce and third bounce is the time between the first bounce and second bounce decreased by a factor of ee.

So the time between the second and third is 1.6e×e1.6e \times e.

The time between the third and fourth is the time between the second and third decreased by a factor of ee.

So the time between the third and fourth is (1.6e×e)×e(1.6e \times e) \times e.


How do we know the time between the second and third bounce decreases by a factor e though..??
Does anyone else know ..?
Original post by Mathematicus65
Does anyone else know ..?


Vertically:

Using

s=ut+12at2s=ut+\frac{1}{2}at^2

for consecutive times the ball hits the ground, we have s=0 and so:

0=ut12gt20=ut-\frac{1}{2}gt^2

and t=0t=0 or t=2ugt=\frac{2u}{g}

t=0 is the start of the bounce, and the time to next hitting the ground is t=2ugt=\frac{2u}{g}.

I.e tu t\propto u

Since u is scaled by a factor of e each time, it follows that t is as well.

Quick Reply

Latest