Successive impacts Quiz

1. A particle hits a fixed wall at right angles at $10$ m s$^{-1}$, with $e=0.3$. Find its speed after the impact.

• A. $3$ m s$^{-1}$
• B. $7$ m s$^{-1}$
• C. $\frac{10}{3}$ m s$^{-1}$
• D. $13$ m s$^{-1}$

2. After a collision, $B$ moves towards a fixed wall at $4$ m s$^{-1}$. The coefficient of restitution between $B$ and the wall is $0.5$. Describe $B$'s motion after hitting the wall.

• A. $2$ m s$^{-1}$ towards the wall
• B. $2$ m s$^{-1}$ away from the wall
• C. $8$ m s$^{-1}$ away from the wall
• D. $4$ m s$^{-1}$ away from the wall

3. After collisions, $A$ moves at $3$ m s$^{-1}$ and $B$ moves at $2$ m s$^{-1}$ in the same direction, with $A$ behind $B$. Will they collide again?

• A. No, since they move in the same direction
• B. No, because momentum is conserved
• C. Yes, since $A$ is faster and behind $B$
• D. Yes, but only if $e=1$

4. A $2$ kg particle hits a fixed wall at $6$ m s$^{-1}$ with $e=\frac12$. Find the magnitude of the impulse of the wall on the particle.

• A. $6$ N s
• B. $9$ N s
• C. $12$ N s
• D. $18$ N s

5. A ball hits a fixed wall at right angles, with $e=0.6$. What fraction of its kinetic energy is retained?

• A. $0.6$
• B. $0.36$
• C. $0.4$
• D. $0.84$