PS 4 A lift travels up and down between the ground art of floor (G) and the roof garden (R) of a hotel. It starts from rest, takes 5s to increase its speed uniformly to 2ms-1, maintains this speed for 5s and then slows down uniformly to rest in another 5s. In the following questions use upwards as positive. (i) Sketch a velocity-time graph for the journey from G to R. On one occasion the lift stops for 5s at R before returning to G. (ii) Sketch a velocity-time graph for this journey from G to R and back. (iii) Calculate the acceleration for each 5 s interval. Take care with the signs. (iv) Sketch an acceleration-time graph for this journey