**Q4: **

A body of variable mass is moving along a fixed straight line. Its mass at time is given by the relation and its displacement is given by the relation , where is a unit vector parallel to the direction of its motion. Determine the bodyβs momentum and the force that is acting on it .

- A ,
- B ,
- C ,
- D ,

**Q5: **

Determine the mass of a body whose momentum is 37 kgβ m/s, given that its displacement vector is given by the relation , where is measured in meters and in seconds.

- A 1β480 g
- B 3β700 g
- C 185 g
- D 7β400 g