Astationary block resting on the ground is pulled up with a tension force of 100n, but does not leave the ground.
if the block weighs 300n. what is the normal force the ground exerts on the block?

The normal force the ground exerts on the block, F = -300 N

Explanation:

Given data,

The block pulled up with a tension force, T = 100 N

The weight of the block, W = 300 N

The weight of the block is due to the force of attraction of gravitation.

The surface exerts a force that is equal and opposite to the force acting on the block due to gravitation.

The weight of the block,

                                  W = mg

                                          300 N

The normal force the ground exerts on the block,

                                  F = - mg

                                    = - 300 N

Hence, the normal force the ground exerts on the block, F = -300 N

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

+15-35=-20

going in opposite directions