(10 points)

3. Use your data from Part 3 and Newton’s laws to explain why the force meter measures a force if the cart is moving at a constant velocity. The forces acting on the cart are the applied force (FA), the force of friction (Ff), weight (Fg) and the normal force (FN). You should cover the following points.
• State Newton’s first law.
• Identify the forces acting on the cart.
• When constant velocity is reached, which pairs of forces are balanced with each other?
• At this point of constant velocity, what is the net force on the cart?
• As you increase mass, what happens to each of the four forces at constant velocity? Why? Are they still balanced?

To answer this question, we need to use Newton's laws and analyze the forces acting on the cart when it is moving at a constant velocity.

1. Newton's first law, also known as the law of inertia, states that an object at rest will stay at rest, and an object in motion will continue moving in a straight line at a constant velocity unless acted upon by an external force. In other words, if the cart is already moving at a constant velocity, it will continue doing so unless another force acts on it.

2. The forces acting on the cart include:
- The applied force (FA): This is the force applied to the cart, such as pushing or pulling it.
- The force of friction (Ff): This is the opposing force that acts between two surfaces in contact, which in this case is the friction between the cart's wheels and the surface it is moving on.
- Weight (Fg): This force is due to the gravitational pull acting on the cart, causing it to have weight.
- The normal force (FN): This is the force exerted by a surface to support an object, acting perpendicular to the surface.

3. When the cart reaches a constant velocity, this means that the acceleration is zero. According to Newton's second law (F=ma), if the acceleration is zero, then the net force acting on the cart must also be zero.

4. At this point of constant velocity, the pairs of forces that are balanced with each other are the applied force (FA) and the force of friction (Ff). The applied force is responsible for maintaining the constant velocity, while the force of friction is opposing it. So, when the cart is moving at a constant velocity, these two forces are equal in magnitude and opposite in direction, balancing each other.

5. The net force on the cart at constant velocity is zero. Since the applied force and force of friction are equal in magnitude and opposite in direction, they cancel each other out, resulting in no net force. This means there are no unbalanced forces acting on the cart to change its motion.

6. As you increase the mass of the cart while maintaining a constant velocity, the forces at play would still be balanced. The applied force (FA) would need to be increased to overcome the increased force of friction (Ff) caused by the higher mass. The weight (Fg) and the normal force (FN) would also increase due to the increased mass, but they do not directly affect the constant velocity. As long as the applied force is adjusted to overcome the increased force of friction, the forces remain balanced, and the cart can still maintain its constant velocity.

In summary, the force meter measures a force when the cart is moving at a constant velocity because the applied force and the force of friction are balanced. At constant velocity, the net force on the cart is zero as long as the applied force is adjusted to counterbalance the force of friction. Increasing the mass will affect the magnitude of the forces, but as long as the applied force is adjusted accordingly, the forces will remain balanced.