A particle P moves in a straight line such that, t s after leaving a point O, its velocity v m s⁻¹ is given by v = 36t –3t² for t ≥ 0.
- (i)Find the value of t when the velocity of P stops increasing.[2]
- (ii)Find the value of t when P comes to instantaneous rest.[2]
- (iii)Find the distance of P from O when P is at instantaneous rest.[3]
- (iv)Find the speed of P when P is again at O.[4]
Mark scheme
Marking points from the official mark scheme (May/June 2013). The mark or mark type is shown in brackets.
- [1] M1 attempt to differentiate and equate to zero
- [1] When dv/dt = 0, t = 6 A1
- [1] M1 for equating v to zero and attempt to solve
- [1] When v = 0, t = 12 A1
- [1] M1 for a correct attempt to integrate at least one term, allow unsimplified
- [1] A1 for all correct
- [1] When t = 12, s = 864 A1 for s = 864
- [1] M1 for substitution of s = 0 into their s equation
- [1] √A1 on their s
- [1] DM1 for substitution of their t back into v equation
- [1] A1 for 324 only
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