You begin bouncing up and down on the trampoline. As you land on the trampoline during one of the bounces, its surface distorts downward 30 cm. While you are in the air above the trampoline, nothing is pushing on you except gravity. While you are touching the trampoline during a bounce, its surface is pushing upward on you. Near the bottom of the bounce, you distort the trampoline's surface downward more than 10 cm.
Bumper cars are a popular ride at many amusement parks.
You drive about an enclosed area in a small, electrically powered vehicle. This vehicle has a large rubber bumper wrapped all the way around its exterior. Half the fun of driving a bumper car is crashing into other people's cars. When you drive forward at high speed and slam into the car in front of you, you find yourself thrown forward in your car. When you are stopped and someone else slams into the front of your car, you find yourself thrown forward in your car.