During a certain time interval, a 20-n object free-falls 10 meters. the object gains joules of kinetic energy during this interval

200 J

Explanation:

By the law of conservation of energy, the kinetic energy gained by the object during the fall is equal to the loss of gravitational potential energy:

The loss of gravitational potential energy of the object over a distance of 10 m is given by:

where

(mg) = 20 N is the weight of the object

h = 10 m is the loss in height

Substituting, we find

So, the kinetic energy gained by the object is

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