A particle P is projected vertically upwards with speed 25 m s⁻¹ from a point 3 m above horizontal ground.
- (i)Find the time taken for P to reach its greatest height.[2]
- (ii)Find the length of time for which P is higher than 23 m above the ground.[3]
- (iii)P is higher than h m above the ground for 1 second. Find h.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.
- [M1] Use of v = u + at with u = 25, v = 0 and a = -g or other complete method for finding t to highest point
- [A1] t = 2.5
- [M1] Applying s = ut + ½at² with s = 20, u = 25
- [M1] Solve a 3-term quadratic for t, factorising or formula
- [A1] Required time = 4 – 1 = 3 seconds
- Alternative method for question 2(ii)
- [M1] Using v² = u² + 2as with u = 25, s = 20 and a = -g
- [M1] Use v at s = 20 to find the time, T, taken to reach the maximum height and to return to s = 20
- [A1] Required time = 1.5 + 1.5 = 3 seconds
- [M1] Using their t from 2(i) – 0.5 in s = ut + ½at² Allow finding h without taking note of the additional 3 m
- [A1] h = 33 m
- Alternative method for question 2(iii)
- [M1] For attempting to find both the maximum height and the distance fallen in 0.5 seconds
- [A1] h = 31.25 – 1.25 + 3 = 33 m
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