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Nov 2018 p43 q3
3624
A particle of mass 1.2 kg moves in a straight line AB. It is projected with speed 7.5 m s-1 from A towards B and experiences a resistance force. The work done against this resistance force in moving from A to B is 25 J.
Given that AB is horizontal, find the speed of the particle at B.
It is given instead that AB is inclined at 30° below the horizontal and that the speed of the particle at B is 9 m s-1. The work done against the resistance force remains the same. Find the distance AB.
Solution
(i) Using the work-energy principle, the change in kinetic energy is equal to the work done against resistance: