Newtons laws of motion
1st law an object in motion tends to stay in motion an object in rest tends to stay in rest unless acted upon an outside force 2nd law acceleration depends onthe objects mass and the amount of net force applied to it 3rd law for every action force there is an equal and opposite reaction force.
Mass with speed equals momentum.More mass means more momentum.Total momentum does not change when objects collide.
Whithout upward force of the ground you feel weightlessness.Skydivers and astronauts feel wieghtlessness.Astronauts move foward but no force slows them down.
action and reaction forces
When a tennis player hits a ball with the racket the ball puts a force on the racket.The racket puts an equal and opposite force on the ball.