Forces at Play:
* Force of Friction: When the tonga is at rest, there is static friction acting on it. This is a force that opposes the initiation of motion. It's stronger than kinetic friction, which acts on a moving object.
* Force of Acceleration: To get the tonga moving, the horse needs to overcome static friction. This requires a greater force than just maintaining its speed once it's in motion.
* Force of Inertia: An object at rest tends to stay at rest, and an object in motion tends to stay in motion. This is inertia. The horse needs to overcome this tendency to start the tonga moving.
How It Works in Practice:
Imagine the horse pulling on the tonga. Initially, the tonga won't budge because the horse's force is not enough to overcome static friction. The horse needs to pull harder to get the tonga moving. Once the tonga is moving, the horse only needs to overcome kinetic friction, which is weaker. So, the horse can apply less force to keep the tonga going at a steady speed.
Key Takeaway:
The horse has to apply more force to start the tonga moving because it has to overcome both static friction and inertia. Once the tonga is in motion, the horse only has to overcome kinetic friction, which requires less force.