A-LevelMathematicsMechanics9709/51 · Oct/Nov 2018 · Q14 Marks
A small ball B is projected with speed 30ms¯¹ at an angle of 60° to the horizontal from a point on horizontal ground. Find the time after projection when the speed of B is 25 m s¯¹ for the second time.
- A small ball B is projected with speed 30ms¯¹ at an angle of 60° to the horizontal from a point on horizontal ground. Find the time after projection when the speed of B is 25 m s¯¹ for the second time.[4]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.
- [M1] v² = 25² – (30cos60)² (v = vertical velocity at the required point)
- [A1] v = (±) 20
- [M1] -20 = 30sin60 – gt (Use v = u + at vertically)
- [A1] t = 4.6(0) s
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