Physics 9702 · AS & A Level · Linear momentum and its conservation
Linear momentum and its conservation — practice question
In the overhead diagrams in Fig. 4.1 and Fig. 4.2, ball Y travels over a horizontal frictionless surface and strikes ball Z. Ball Y has a mass of $0.25\,\text{kg}$ and is initially moving along line PQ. Ball Z has mass $m_Z$ and is initially at rest. After the collision, ball Y has a final velocity of $3.7\,\text{m s}^{-1}$ at an angle of $27^\circ$ to line PQ, and ball Z has a final velocity of $5.5\,\text{m s}^{-1}$ at an angle of $44^\circ$ to line PQ.
(a(i))[2]
Calculate the component of ball Y’s final momentum that is perpendicular to line PQ.
(a(ii))[1]
Using the perpendicular component of the final momentum of each ball, calculate $m_Z$.
(a(iii))[2]
During the collision, the average force on Y from Z is $F_Y$ and the average force on Z from Y is $F_Z$. Compare the magnitudes and directions of $F_Y$ and $F_Z$. Numerical values are not required.
(b)[1]
Two blocks, A and B, move directly towards one another over a horizontal frictionless surface, as shown in the view from above in Fig. 4.3. The blocks collide perfectly elastically. Before the collision, block A has a speed of $4\,\text{m s}^{-1}$ and block B has a speed of $6\,\text{m s}^{-1}$. After the collision, block B moves back along its original path with a speed of $2\,\text{m s}^{-1}$. Calculate the speed of block A after the collision.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “perpendicular component of momentum $=0.25\times3.7\times\sin27^\circ$” …