Three point masses lie on a straight friction-free track
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Three point masses lie on a straight friction-free track. A 6.0kg mass and a 9.0kg mass are fixed in place, with their centers 0.40m apart. A 3.0kg cart is initially held at rest at the point midway between them.
Ignore all forces except the mutual gravitational attractions among the three objects.
(a) Calculate the magnitude and direction of the net gravitational force acting on the 3.0kg cart while it is held midway between the two fixed masses.
(b) The cart is released from rest. Determine its instantaneous acceleration at the moment of release, stating both magnitude and direction.
(c) Briefly explain why the larger of the two fixed masses exerts the dominant influence on the cart’s motion, even though the distances involved are equal.