Explain why, in terms of forces, there is a risk of head injury when diving from this height. Suggest why the high divers would choose to enter the water feet first.

What is the angular momentum of the bar about the axle?

Consider a system with two masses that are moving away from each other. why will the kinetic energy differ if the frame of reference is a stationary observer or one of the masses?

Ahot-air balloon takes off from the ground traveling vertically with a constant upward acceleration of magnitude g/4. after time interval δt, a crew member releases a ballast sandbag from the basket attached to the balloon. how many seconds does it take the sandbag to reach the ground? (express your answer in terms of δt)