The curved line PQR is the velocity-time graph for a car starting from rest. velocity
What is the average acceleration of the car over the first 5s?
The area below the curve PQ
The area of the triangle PQS
The gradient of the straight line PQ
The gradient of the tangent at Q​

Amachinist turns the power on to a grinding wheel, at rest, at time t = 0 s. the wheel accelerates uniformly for 10 s and reaches the operating angular velocity of 96 rad/s. the wheel is run at that angular velocity for 40 s and then power is shut off. the wheel slows down uniformly at 1.5 rad/s2 until the wheel stops. in this situation, the time interval of deceleration is closest to: