OCR A Level: Mechanics 2 - Projectile Motion [June 2009 Q7]

A ball is projected with an initial speed of $17 \text{m s}^{-1}$ at an angle of $25°$ below the horizontal from a point on the top of a vertical wall. The point of projection is $8 \text{m}$ above horizontal ground. The ball hits a vertical fence which is at a horizontal distance of $9 \text{m}$ from the wall (see diagram).

$(\text{i})$ Calculate the height above the ground of the point where the ball hits the fence.

$(\text{ii})$ Calculate the direction of motion of the ball immediately before it hits the fence.

$(\text{iii})$ It is given that 30% of the kinetic energy of the ball is lost when it hits the fence. Calculate the speed of the ball immediately after it hits the fence.

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Input your answer to part $(\text{iii})$ , correct to 3 significant figures.

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There are 5 marks available for part (i), 5 marks for part (ii) and 4 marks for part (iii).

In total, this question is worth 19.4% of all available marks in the paper.

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This is part of the set OCR A Level Problems .