A firework rocket is launched straight upwards. Its fuel burns and gives the rocket a steady upward force. Once $5\,\text{s}$ have passed, all the fuel has been used up. Air resistance is negligible. What is the acceleration before and after $5\,\text{s}$?
- Abefore $5$ seconds: constant; after $5$ seconds: constant
- Bbefore $5$ seconds: constant; after $5$ seconds: zero
- Cbefore $5$ seconds: increasing; after $5$ seconds: constant
- Dbefore $5$ seconds: increasing; after $5$ seconds: zero