The police officer is 50 metres behind the chain snatcher. The chain snatcher runs at 2 m/s and the police officer runs at 4 m/s.
The police officer closes the gap at the difference of their speeds:
Gap closing speed =4−2=2 m/s
The time required to close the 50 metre gap:
Time =Gap closing speedDistance gap
Time =250=25 seconds
The distance covered by the chain snatcher in 25 seconds:
Distance =Speed×Time
Distance =2×25
Distance =50 metres
At the moment of catching:
- Chain snatcher position: 50+50=100 metres from starting point
- Police officer position: 0+(4×25)=100 metres from starting point
Therefore, the chain snatcher covers 50 metres before being caught.