A worker of mass 70 ,kg stands on a platform of mass 15 ,kg
PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
A worker of mass 70\,kg stands on a platform of mass 15\,kg. A light, inextensible rope is attached to the platform, runs upward over a smooth pulley fixed to the ceiling, and returns to the worker’s hands, so that he can pull on the free end and lift himself along with the platform. While pulling, the worker maintains the tension in the rope at a steady value of 600\,N.
Study the situation and answer the following questions.
(i) Draw separate free-body diagrams for (a) the worker and (b) the platform, indicating all forces acting on each body.
(ii) Identify every action–reaction pair that involves the worker, the rope, the platform and the Earth.
(iii) Using the diagrams, show that the total upward force acting on the platform–worker system is twice the rope tension. Hence determine whether the worker accelerates upward, downward or remains at rest, taking g=9.8ms−2.
(iv) Distinguish between those upward forces on the worker that are members of Newton’s Third Law pairs and those that are not.