Force Diagrams
A force diagram displays all of the different forces acting on an object at one time, whether it be in equilibrium or not. Force diagrams also help calculate the net force, or total amount of force acting on an object.
In this case, all of the forces acting on the object counteract eachother, making the net force zero. Therefore, the object is in equilibrium. If the object is moving at a constant speed, this is called dynamic equilibrium, but does not necessarily mean all forces (vertical and horizontal) are the same. If the object is moving at a constant speed there is more applied force than there is normal or gravity, but friction counteracts it, leaving the net force at zero. Static equilibrium is where all the forces, both vertical and horizontal all amount to the same measurement, leaving the object completely still.
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In relation to Sanic, the same can be said for him. When Sanic runs, more applied force is acting on him to get him moving than there is friction acting on him. He is not in equilibrium. In this case, the support force and gravity would cancel each other out, but, assuming the applied force is 60 Newtons and friction is 20 Newtons, the net force would be 40 Newtons to the right.
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Review Questions
1. If gravity is pushing down on a man with a force of 800 Newtons and the man is not moving, how much force is being returned by the ground (support force)?
800N
2. If Sanic is holding onto two ropes suspending him up in the air and Sanic weighs 342 N, how much force is acting on each of the ropes?
171 N
800N
2. If Sanic is holding onto two ropes suspending him up in the air and Sanic weighs 342 N, how much force is acting on each of the ropes?
171 N