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

Classical Mechanics Level pending

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.

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

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