Question

A body is moving under the action of two forces $ {{\overrightarrow{F}}_{1}}=2\hat{i}-5\hat{j};{{\overrightarrow{F}}_{2}}=3\hat{i}-4\hat{j} $ Its velocity will become uniform under a third force $ {{\overrightarrow{F}}_{3}} $ given by

• A. $ 5\hat{i}-\hat{j} $
• B. $ -5\hat{i}-\hat{j} $
• C. $ 5\hat{i}+\hat{j} $
• D. $ -5\hat{i}+9\hat{j} $

Answer 1

Answer: (D)

: For uniform velocity, accleration is zero. Hence resultant force will be zero $ \therefore $ $ {{\overrightarrow{F}}_{1}}+{{\overrightarrow{F}}_{2}}+{{\overrightarrow{F}}_{3}}=0 $ $ (2\hat{i}-5\hat{j})+(3\hat{i}-4\hat{j})+{{\overrightarrow{F}}_{3}}=0 $ Or $ {{\overrightarrow{F}}_{3}}=(-5\hat{i}+9\hat{j}) $