Question

Three children are fighting over a toy cart. Child A pushes from the $+y$ direction towards the $-y$ direction with $40N$ of force, while Child B pushes from the $-x$ direction towards the $+x$ direction with $30N$ of force.
If the toy cart is not moving, how much force (in magnitude) must Child C be pushing the cart with?

• A. $10N$
• B. $20N$
• C. $30N$
• D. $40N$
• E. $50N$

Answer 1

Answer: (E)

$50N$

Since the forces act perpendicular to each other, the resultant of the two forces is $\sqrt{{40}^2+{30}^2}N=50N$

The cart does not move with third child applying the force. Hence he must be applying force equal in magnitude of the calculated resultant force in opposite direction of the force.

Hence correct answer is option E.