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# M1 Question watch

1. A ball is projected vertically upwards with a speed u m s−1 from a point A which is 1.5 m above the ground. The ball moves freely under gravity until it reaches the ground. The greatest height attained by the ball is 25.6 m above A.
(a) Show that u = 22.4.
(3)
The ball reaches the ground T seconds after it has been projected from A.
(b) Find, to 2 decimal places, the value of T.

The ground is soft and the ball sinks 2.5cm into the ground before coming to a rest. The mass of the ball is 0.6kg. The ground is assumed to exert a constant resistive force of magnitude F newtons.

(c) Find, to three significant figures, the value of F.

I've got part a) and part b).

However for part c, the solution splits up the question into 2 parts, one being the speed at which the ball hits the ground at. Why is it not possible to use the original value for the initial velocity(22.4) for part c)?

That's really all I need to know, from there I get the method.
2. Beacuse that's not the speed at which it strikes the ground, but rather the speed 1.5m above the ground.

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Updated: March 6, 2018
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