A small mass is set down at point P on the inner surface of a smooth hemisphere, and it is then released from rest. When it arrives at the lowest point T, its speed is $4.0\,\text{m s}^{-1}$. The diagram, which is not to scale, shows the mass’s speed at other points Q, R and S while it slides down. Air resistance is negligible. From P to T, the mass loses potential energy $E$. At which point has the mass lost potential energy $\frac{E}{4}$?
- AQ
- BR
- CS
- Dnone of these