Easy -1.2 This is a straightforward application of conservation of momentum with a single unknown. Students set up momentum before = momentum after (2m = -0.5m + 0.2), then solve a simple linear equation. It requires only recall of a standard formula and basic algebra, making it easier than average.
1 Particles \(P\) of mass \(m \mathrm {~kg}\) and \(Q\) of mass 0.2 kg are free to move on a smooth horizontal plane. \(P\) is projected at a speed of \(2 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) towards \(Q\) which is stationary. After the collision \(P\) and \(Q\) move in opposite directions with speeds of \(0.5 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) and \(1 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) respectively.
Find \(m\).
1 Particles $P$ of mass $m \mathrm {~kg}$ and $Q$ of mass 0.2 kg are free to move on a smooth horizontal plane. $P$ is projected at a speed of $2 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ towards $Q$ which is stationary. After the collision $P$ and $Q$ move in opposite directions with speeds of $0.5 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ and $1 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ respectively.
Find $m$.\\
\hfill \mbox{\textit{CAIE M1 2020 Q1 [3]}}