Suppose you are helping a friend move. The friend asks you stand in the back of a pickup truck to hold a piano because there is no rope available to tie it down. Explain why you should refuse this request.

Explanation:

This exposes the individual to danger. Remember, the Newton Law of motion which says that an object under the state of rest will remain in that state (inertia) unless when acted upon by an external force.

In this scenario, standing at the back of the pickup truck presents danger especially if the truck suddenly stops; this individual would experience an upward thrust due to inertia that may disbalance him.

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me