Remedial Discussion Questions

Linear Motion1. When the velocity is constant, does the average over any time interval differ from the instantaneous velocity at any instant?

2. (a) Can an object have zero velocity and still be accelerating? (b) Can an object have a constant speed and still have a varying velocity?

(c) Can an object have a constant velocity and still have varying speed?

3. A car is accelerating at12 m/s2. Find its acceleration inkm/h2.4. A boy standing at the edge of a cliff of 20 m above sea level, throws a stone straight up with a speed of 25 ms-1 .

(a) How long does it take to reach its highest point?

(b) How high does the ball rise above its release point?

(c) How long will it take for the stone to reach a point 25 m above its release point?

(d) Calculate the velocity of the stone when it hits the water surface.5. A parachutist after bailing out falls 50 m without friction When the parachute opens, he decelerates downwards 2.0 ms-2. He reaches the ground with a speed of 3.0 ms-1.(a) How long is the parachutist in the air?

(b) At what height did he bail out?

6. A body accelerates uniformly from rest along a straight line. Sketch a graph showing how the displacement of the body varies with time. How is the instantaneous velocity of a particle obtained from a graph of displacement against time?

7. A cricketer throws a ball vertically upwards and catches it 3.0 s later. Neglecting air resistance, find

(a) the speed with which the ball leaves his hands

(b) the maximum height to which it rises

(c) Draw a sketch graph showing how the velocity of the ball depends on time during its flight. Mark on your graph the times at which

(i) the ball leaves the cricketers hands

(ii) It comes to its maximum height

(iii) It reaches his hands again

(no need to calculate particular values for velocity)