The correct option is D 3000 N
The net force on a body moving at a constant velocity is zero. The engine and the cart are moving on a rough surface. Therefore, the forward force must be equal to the opposing frictional force, i.e.,
fengine+cart (frictional force acting on engine and cart) = 1000 N
The net force to move the cart with an acceleration of 1 m/s²:
Fnet = 2000 ✖ 1 = 2000 N
Thus, the force required to pull the cart (F) is,
Fnet = F - fengine+cart ⇒ 2000 = F - 1000
⇒ F = 3000 N