A-LevelMathematicsMechanics9709/52 · May/June 2019 · Q15 Marks
A small ball is projected from a point O on horizontal ground at an angle of 30° above the horizontal. At time t s after projection the vertically upwards displacement of the ball from O is (14t – kt²) m, where k is a constant.
- (i)State the value of k.[1]
- (ii)Show that the initial speed of the ball is 28 m s⁻¹.[2]
- (iii)Find the horizontal displacement of the ball from O when t = 3.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.
- [B1] k = g/2 = 5
- [M1] Use the trajectory equation from the formula sheet
- [A1] AG
- [M1] Use horizontal motion. Allow their V for M1
- [A1]
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