Question

A man is pulling a box attached to a string at some angle with horizontal as shown in above figure. Both the person and the box are moving to the right with a constant velocity, $v$. Identify the horizontal forces which are acting on the person?

• A. The tension force in the string is pulling the person to the left
• B. The tension force in the string is pulling the person to the left, and the Earth is pushing the person to the right
• C. The tension force in the string is pulling the person to the left, and the Earth is pushing the person to the left
• D. The tension force in the string is pushing the person to the right, and the Earth is pushing the person to the right
• E. The tension force in the string is pushing the person to the right, and the Earth is pushing the person to the left

Answer 1

Answer: (B)

The tension force in the string is pulling the person to the left, and the Earth is pushing the person to the right

Person is in contact with earth and the string. So only these two can apply forces on the man. Tension of the string pull the man towards left and since he is moving with constant velocity the earth must be apply force on him towards right so that the total force on him becomes zero.