PHYSICS · Single correct · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
Two identical carts are connected by a light, inextensible string and pulled to the right on a frictionless track by a constant external force Fpull applied to the front cart. A student models the two carts together as a single system. Which of the following best explains why the tension in the string does not affect the system’s acceleration in this model?
(a) The tension is much smaller than the applied force, so it can be neglected when finding the system’s acceleration.
(b) The string’s tension acts internally, so the forces it exerts come in equal-and-opposite pairs that cancel within the system.
(c) Because the string is ideal, the tension has the same magnitude everywhere, so its contributions cancel out and it produces no net acceleration.
(d) A massless, inextensible string cannot sustain any force, so its tension is zero and thus does not affect the acceleration.