Question:
An apple falls from a tree because of gravitational attraction between the earth and apple. If $F_{1}$ is the magnitude of force exerted by the earth on the apple and $F_{2}$ is the magnitude of force exerted by apple on earth, then
(a) $F_{1}$ is very much greater than $F_{2}$
(b) $F_{2}$ is very much greater than $F_{1}$
(c) $F_{1}$ is only a little greater than $F_{2}$
(d) $F_{1}$ and $F_{2}$ are equal.
Solution:
(d) Explanation: $\overrightarrow{\mathrm{F}}_{1}=-\overrightarrow{\mathrm{F}}_{2}$.