Question

A horse continues to apply a force in order to move a cart with a constant
speed. This is because:

• A. the force applied by the horse balances the gravitational force.
• B. the force applied by the horse balances the force of friction.
• C. Horse does not apply any force.
• D. None of these

Answer 1

The correct option is B the force applied by the horse balances the force of friction.

A horse is harnessed to a cart. If it exerts a force on ( or pulls ) the cart, then by the $\text{Newton's Third Law of Motion}$ the cart must then exert an equal and opposite force on the horse.

For the horse to move with constant velocity, hence zero net acceleration, the $\text{frictional force}$ acting on him from the surface and the mechanical force it applies on the art should and indeed balance each other.

So, B. The force applied by the horse balances the force of friction.