7. A bullet of mass 100 g is fired into a stationary target of mass 4.o kg. The target is mounted on low-friction wheels and moves off at a velocity of 5.0 ms-1 when the bullet enters it. The bullet stays in the target. Calculate the velocity of the bullet before it strikes the target.

Awater balloon launcher uses an elastic band with a spring constant of 115 n/m to use thee launcher you stretch thee band back with a balloon n it the water balloons have a mass of 1.3 kg a) if you stretch the band by 0.8 m, what elastic force will the band exert? b) with the band stretched 0.8 m, how much elastic potential energy is stored in the spring? c) if you release the band, it pushes forward. what is the kinetic energy of the balloon when it reaches the natural length of the band? d) what is the speed of the balloon when it reaches the natural length of the band?