JAMB Physics 2018 Paper

Concept:Change in momentum is the product of mass and the change in velocity of the body.Explanation:Take the direction towards the wall as positive.Initial velocity, $u = +10 \, \mathrm{m\,s^{-1}}$.Final velocity after rebounding, $v = -2.0 \, \mathrm{m\,s^{-1}}$ because it moves in the opposite direction.Mass, $m = 100 \, \mathrm{g} = 0.1 \, \mathrm{kg}$.Change in momentum is given by:$$\Delta p = m(v - u)$$Substitute the values:$$\Delta p = 0.1(-2.0 - 10)$$$$\Delta p = 0.1(-12) = -1.2 \, \mathrm{N\,s}$$The magnitude of the change in momentum is $1.2 \, \mathrm{N\,s}$.Answer:B. $1.2 \, \mathrm{Ns}$