classic footage of the Apollo 11 astronauts show them taking large leaps bounding around the surface of the moon. By transporting this simple spring and mass system to the moon, we can measure the gravitational force exerted by the moon on objects at its surface and compare it to the force of gravity exerted by the earth on people at its surface. i. Use the apparatus to measure the force of gravity exerted by the moon on the 50 gram mass. What is the value of this force

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

third one with arrows on top of each other going the same direction