A police officer points a laser gun from a moving police car at the back of a car that is passing at great speed. when the laser gun emits the first pulse, the car is 60 m in front of the police car. the speed of the police car is 80 km/h. A. calculate the time between sending the pulse and registering the reflected pulse. neglect the movement of the car relative to the police car during this time.
B. calculate the speed of the moving car in km/h.
Can you please help me. my teacher ignores me.

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?