A particle P of mass 0.4 kg is projected vertically upwards from horizontal ground with speed 10ms-1.
- (a)Find the greatest height above the ground reached by P.[2]
- (b)When P reaches the ground again, it bounces vertically upwards. At the first instant that it hits the ground, P loses 7.2 J of energy. Find the time between the first and second instants at which P hits the ground.[4]
Mark scheme
Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.
- [M1] For use of v² = u² + 2as with v = 0, u = ±10 and a=±g or ±10 and solve for s (or any other complete SUVAT method). Or using an energy method: 0.4gh = ¹/₂(0.4)(10)² and solve for h (with two terms using correct given values – condone lack of masses in conservation of energy equation).
- [A1]
- [B1FT] Or loss of PE = ± 0.4 × g × 5 using their maximum height from (a).
- [*M1] M1 for ¹/₂×0.4v² = KE/PE before impact – 7.2 (must be correct method of subtracting 7.2 (OE)). Or, for finding the maximum height after first impact. Need not solve for v (or h) for this mark.
- [DM1] For use of a complete method to find t. Condone sign errors but a = ±g. If calculating the time to the maximum height between the first and second impacts, then candidates must double this answer (OE). E.g., 0=8+(-g)T, t = 2T = ... or 3.2 = 0-0.5x-gxT² ⇒ t = 2T = ....
- [A1]
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