As jack pulls his wagon down the street it moves faster and faster. jill, sitting a few meters ahead on the sidewalk, wants to slow jack's wagon down so that it travels with a constant speed. how can jill accomplish her goal?

D) She can pull the wagon in the opposite direction with a force equal to Jack's.

Explanation:

If you exert a force that is equal to that of another force being applied to an object, the object will not be accelerating. Since Jack is pulling the wagon faster and faster, the object is accelerating, but if Jill exerts the same force as Jack is exerting, the object would be balanced and have no Newtons acting on it allowing it to move at a constant speed. All the other options would cause for an acceleration or deceleration to take place. If she sat in the wagon, it would not move at a constant speed, if she pushed Jack away from the wagon so that he is not pulling on it anymore, the wagon would decelerate and if she pulled the wagon toward her with twice the force, it would accelerate in her direction.

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