9709/May June/2011/42/Q3

The velocity-time graph shown models the motion of a parachutist falling vertically. There are four
stages in the motion:
• falling freely with the parachute closed,
• decelerating at a constant rate with the parachute open,
• falling with constant speed with the parachute open,
• coming to rest instantaneously on hitting the ground.

(i) Show that the total distance fallen is 1048m.
The weight of the parachutist is 850N.
(ii) Find the upward force on the parachutist due to the parachute, during the second stage.

Solution:

Reference: PYQ - May/Jun 2011 Paper 42 Q3

9709/May June/2011/42/Q2

An object of mass 8 kg slides down a line of greatest slope of an inclined plane. Its initial speed at the top of the plane is 3ms−1 and its speed at the bottom of the plane is 8ms−1. The work done against the resistance to motion of the object is 120 J. Find the height of the top of the plane above the level of the bottom.

Solution:

Reference: PYQ - May/Jun 2011 Paper 42 Q2

9709/Oct Nov/2002/4/Q7

A particle P starts to move from a point O and travels in a straight line. At time ts after P starts to

move its velocity is v ms^-1, where v - 0.12t - 0.0006t².

(i) Verify that P comes to instantaneous rest when t = 200, and find the acceleration with which it

starts to return towards O.

(ii) Find the maximum speed of P for 0 <= t <= 200.

(iii) Find the displacement of P from O when t = 200.

(iv) Find the value of t when P reaches O again.

Solution:

 

Reference: PYQ - Oct/Nov 2002 Paper 4 Q7

9709/Oct Nov/2002/4/Q4

Two particles A and B are projected vertically upwards from horizontal ground at the same instant.

The speeds of projection of A and B are 5ms^-1 and 8ms^-1 respectively. Find

(i) the difference in the heights of A and B when A is at its maximum height,

(ii) the height of A above the ground when B is 0.9m above A.

Solution:

Reference: PYQ - Oct/Nov 2002 Paper 4 Q4