question_answer

A force of 5 N changes the velocity of a body from \[\text{1}0\text{ m}{{\text{s}}^{\text{-1}}}\] to \[\text{2}0\text{ m}{{\text{s}}^{\text{-1}}}\]in 5 sec. How much force is required to bring about the same change in 2 sec?

Answer:

                From\[{{F}_{1}}=\frac{dP}{d{{t}_{1}}}\] and \[{{F}_{2}}=\frac{dP}{d{{t}_{2}}}\] \[\frac{{{F}_{2}}}{{{F}_{1}}}=\frac{d{{t}_{1}}}{d{{t}_{2}}}\];           \[{{F}_{2}}={{F}_{1}}\times \frac{d{{t}_{1}}}{d{{t}_{2}}}=\frac{5\times 5}{2}=12.5N\]