Question 1
A stone of mass 20 g is released from a catapult whose rubber is stretched through 5 cm. If the force constant of the rubber is 200 N m-1, calculate the speed with which the stone leaves the catapult.
Observation
Candidates were to calculate the speed of a stone from a catapult. Majority of the candidates recognized that a stretched catapult stores energy (½ke2) which was released as kinetic energy (½mv2). Many of the candidates made the right substitution and converted to S.I unit to score full marks while others did not convert to S.I unit.
The expected response is as stated below:
½ke2 = ½mv2
½ x 200 x (0.05)2 = ½ x 0.02 x v2
v2 = 25
v = 5 m s-1