When cart moves on the road it has to encounter friction. In order to keep the cart moving horse should overcome the friction. Hence it continues to apply the force.
- Newton’s First Law states that a body remains in motion or at rest until an external force acts on it.
- However, in this case, the horse must constantly exert force to move the cart since the force of friction is acting against the cart’s motion and opposing it.
- As a result, the horse must exert force to overcome the frictional force.