Louisa builds the body of a race car out of cardboard. She tapes a straw to the cardboard so that one end of the straw is tilted up and the other end hangs over the back of the car. Then, she places an inflated balloon over the tilted end of the straw and releases the mouth of the balloon to allow air to flow through the straw. The race car rolls forward as the balloon releases air through the straw, as shown in the picture below.

Question

Image courtesy of NASA

How does Louisa's race car demonstrate Newton's third law of motion?
A.
The forward movement of the car forces air to leave the balloon faster.
B.
The balloon pushes the air out, and the air pushes back on the balloon.
C.
The forward movement of the car forces air to leave the balloon slower.
D.
The balloon pushes against the air, which results in a zero net force on the balloon.

Answer 1

Louisa's race car demonstrates Newton's third law of motion with option B. The balloon pushes the air out, and the air pushes back on the balloon.

According to Newton's third law, for every action, there is an equal and opposite reaction. When the balloon pushes air out through the straw, the air exerts a force back on the balloon in the opposite direction, which helps propel the car forward. This interaction between the released air and the balloon illustrates the principle of action and reaction.