Question

If a man walks with constant velocity $-3\hat{i}\text{m/s}$, and a boy is running with constant velocity of $3\hat{i}+4\hat{j}\text{m/s}$, then choose the correct option.

• A. Motion of the man is two dimensional.
• B. Motion of the boy is two dimensional.
• C. Motion of both man and boy, is one dimensional.
• D. Can't say as data is insufficient

Answer 1

The correct option is C Motion of both man and boy, is one dimensional.

As per the question, the velocity of the man is $3m/s$ in the negative $x$ direction, which is in straight line.
Also, the velocity of boy is $\sqrt{3^2+4^2}=5m/s$ at an angle of $\alpha =\tan -1\left(\frac{4}{3}\right)={53}^{\circ }$ from the positive $x$ axis, which is also in straight line.
As we know that, if the path of a particle is straight line, it is one dimensional motion.
Hence, man and boy both have one dimensional motion.