Question 7
Two objects of mass 2 kg and 8 kg are released together from the same height. Ignoring air resistance, what can be said about their accelerations?
The right answer is the one marked above.
Both have the same acceleration. Both accelerate at g = 9.8 m s−2.
The force on the 8 kg object — its weight — is four times as large. But its mass is four times as large as well. In a = F ÷ m the two cancel:
a = m g ÷ m = g
So the acceleration of a freely falling object does not depend on its mass at all. It is the most surprising result in either of these two chapters.