A particle P is projected from the origin O so that it moves in a straight line. At time t seconds after projection, the velocity of the particle, v ms⁻¹, is given by v = 2t² - 14t + 12.
- (i)Find the time at which P first comes to instantaneous rest.[2]
- (ii)Find an expression for the displacement of P from O at time t seconds.[3]
- (iii)Find the acceleration of P when t = 3.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2015). The mark or mark type is shown in brackets.
- [M1] 2t² -14t+12 = 0 Can use formula, etc.
- [A1] (t=) 1 If t = 1 with no working, then M1A1
- [M1] ∫(2t²-14t+12)dt
- [A2,1,0] (s=) (2t³/3) - (14t²/2) + 12t -1 for each error or for +c left in or limits introduced
- [M1] (a=) dv/dt (4t-14)
- [A1] [4(3) - 14 =] -2 cao
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