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In physics, tension refers to the force that is transmitted through a string, cable, or similar object when it is pulled tight by forces acting from opposite ends. It's important to understand that tension is a force that ensures the object stays connected between the two ends.
For example, in the scenario with the stuntman, the tension in the cable ensures that the stuntman is being dragged along the road. When dealing with tension, the force is directed along the length of the medium, in this case, the cable, and away from the object being pulled.

• **Consistency:** In this problem, the fact that the stuntman is moving at a constant velocity indicates that the force due to tension equals the kinetic frictional force.
• **Direction:** Tension acts parallel to the ground, emphasizing why the understanding of direction is crucial in physical dynamics scenarios.

Overall, calculating tension accurately requires balancing all forces involved to determine the resultant force that establishes equilibrium in the system.

The gravitational force, often referred to as "weight," is the force with which the Earth pulls on an object. It's calculated using the formula:
\[ F_g = m \, g \]
Where:

• \( F_g \) is the gravitational force
• \( m \) is the mass of the object (for the stuntman, it is 109 kg)
• \( g \) is the acceleration due to gravity, approximately 9.8 m/s² on Earth.

Gravitational force plays a crucial role in determining other forces acting on the stuntman; it directly influences the normal force exerted by the ground.
The gravitational force keeps the stuntman grounded, opposing the drag force due to friction. It acts vertically downward and is crucial for calculating other forces in physics problems, as it typically influences the normal force and friction.

The normal force is the perpendicular contact force exerted by a surface on an object in contact with it. In our stuntman example, this is the force of the road pushing up against the stuntman’s body, balancing the gravitational force pulling him down.
Key points to remember about normal force include:

• **Equilibrium on Flat Surfaces:** On a horizontal surface and with no vertical acceleration, the normal force should balance the gravitational force. That means it has equal magnitude but acts in the opposite direction to weight.
• **Changes with Inclines and Other Forces:** While on flat ground in this exercise, the normal force is equal to the gravitational pull \( N = 1068.2 \, N \). On inclined surfaces or if there are vertical accelerations, calculating normal force can become more complex.

Understanding normal force is essential for analyzing scenarios involving friction and contact forces in physics, as it directly affects how much frictional force can be developed, thus influencing the tension needed to maintain motion.