A 5 kg skateboard is pushed by a student exerting a 40 N force on it. By Newton's Third Law, the skateboard exerts a 40 N force back on the student. Why does the student move less than the skateboard?

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Question

A 5 kg skateboard is pushed by a student exerting a 40 N force on it. By Newton's Third Law, the skateboard exerts a 40 N force back on the student. Why does the student move less than the skateboard?

Accepted Answer

The student has greater mass, so the same force produces less acceleration — Newton's Second Law (a = F/m) shows that equal forces produce different accelerations in objects of different mass. The student has much greater mass than the 5 kg skateboard, so the equal 40 N reaction force produces a smaller acceleration in the student. Option A incorrectly states the forces are unequal — Third Law forces are always equal. Option C is a classic misconception; action-reaction forces act on different objects and cannot cancel. Option D reverses the effect of friction and misapplies it.

Answer

Friction only acts on the skateboard, reducing its acceleration more

Answer

Action-reaction forces cancel out, so neither object should accelerate

Answer

The student has greater mass, so the same force produces less acceleration

Answer

The force on the student is smaller than the force on the skateboard

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