(a) Find ( v(t) ) (3 marks) (b) Find ( s(t) ) (3 marks) (c) Calculate the total distance travelled between ( t = 1 ) and ( t = 4 ) seconds, explaining how you treat any change of direction. (3 marks) Q1 (a) ( v(t) = \int (6t - 4), dt = 3t^2 - 4t + C ) ( v(0) = 5 \Rightarrow C = 5 ) [ v(t) = 3t^2 - 4t + 5 ]
(c) Check if ( v(t) = 0 ) in [1,4]: ( v(t) = 4t^3 - 4t^2 + 2t + 3 ) Test ( t=1 ): ( 4 - 4 + 2 + 3 = 5 >0 ) Test ( t=0 ): ( 3 >0 ), cubic positive, likely no root. Check derivative: ( 12t^2-8t+2>0 ) (discriminant 64-96<0) so ( v(t) ) increasing, always positive. No change of direction. --- Integral Variable Acceleration Topic Assessment Answers
(b) ( s(t) = \int (4t^3 - 4t^2 + 2t + 3) dt = t^4 - \frac{4t^3}{3} + t^2 + 3t + D ) ( s(1) = 1 - \frac{4}{3} + 1 + 3 + D = 5 - \frac{4}{3} + D = \frac{15}{3} - \frac{4}{3} + D = \frac{11}{3} + D = 3 ) ( D = 3 - \frac{11}{3} = -\frac{2}{3} ) [ s(t) = t^4 - \frac{4t^3}{3} + t^2 + 3t - \frac{2}{3} ] (a) Find ( v(t) ) (3 marks) (b)
(b) ( v(t) = 0 \Rightarrow \frac{t^2}{2}\left(3 - \frac{t}{3}\right) = 0 ) ( t = 0 ) or ( t = 9 ) seconds (answer: ( t = 9 )) No change of direction
Distance ( = s(4) - s(1) ) ( s(4) = 256 - \frac{256}{3} + 16 + 12 - \frac{2}{3} ) ( = 284 - \frac{258}{3} = 284 - 86 = 198 ) ( s(1) = 3 ) (given) [ \text{Distance} = 198 - 3 = 195 \ \text{m} ]
(b) ( s(t) = \int (3t^2 - 4t + 5), dt = t^3 - 2t^2 + 5t + D ) ( s(0) = 2 \Rightarrow D = 2 ) [ s(t) = t^3 - 2t^2 + 5t + 2 ]