The article discusses about the comparative analysis and detailed facts of net force vs force.
|We talk about only a single force acting on an object.||We talk about the multiple forces acting on an object.|
|It acts in a single direction.||It acts in all possible directions.|
|It is either only the action or reaction force.||It includes both action and reaction forces.|
|Newton’s first law of motion says that an object remains at rest or in motion unless acted upon by force||Newton’s second law says that the net force accelerates an object having mass by changing its motion.|
Read more about Types of Forces.
The ball is at rest as there is no force. We apply a certain force to the ball by throwing it that accelerates its motion.
As per Newton’s third law, the air also exerts the drag force as a reaction force which decelerates the ball’s motion. Both forces acting on the ball are attempting to change our motion individually.
So what will we do if several forces act?
We substitute the effects of each force on the ball’s motion by summing up or adding all the forces to give net force on us as,
Fnet = F1 + F2
As per Newton’s second law of motion,
Fnet = ma
Correcting Newton’s first law,
“Any object of mass m at rest stays in rest or motion stays in constant motion unless it is acted upon by net force Fnet.”
Read more about Newton’s Laws.
Net Force Vs Applied Force
|Net Force||Applied Force|
|It acts in any direction. Hence it might be positive or negative.||It always acts in a forward direction. Hence it is always positive.|
|It includes both action and reaction forces.||It is always an action force.|
|It includes both contact and non-contact forces.||It is a contact force exerted when two surfaces come in contact.|
|Newton’s third law says that the reaction force tries to oppose the motion which accelerates by the action force.||Newton’s first law says that the applied force accelerates an object by changing its motion.|
We are required to apply push force to move the box on the floor. An object is either at rest or in motion; there must be a gravity force exerted downward to an object. When we push the box along the ground, the ground exerts the normal force opposite the gravity force and the friction force opposite the applied force.
Read more about Sliding Friction.
So what will the ball’s direction be if multiple forces act on it?
Force is a vector, and it has direction and magnitude. So the force accelerates any object along with its direction. But when several forces act on the same object, they set its different accelerations in different directions. That’s why we summed all forces as one net force that determines an object’s acceleration and direction.
Considering the applied force F1 and friction Force F2 as Horizontal forces Fhorz as pair of forces acted on the box horizontally,
and the normal force F3 andgravity force F4 as Vertical forces Fvert as a pair of forces acted on the box vertically.
Fnet = Fhort + Fvert
Fnet = (F1+F2) + (F3+F4)
Since friction force F2 and gravity force F4 act opposite the box, their signs are negative. Therefore,
Fnet = (F1-F2) + (F3-F4) ……………….. (*)
Read more about Work done by Friction.
Unbalanced Force Vs Net Force
|Unbalanced Force||Net Force|
|It is either action or reaction force but related to both forces.||It contains both action force and reaction force.|
|It corresponds to either horizontal forces or vertical forces.||It corresponds to both horizontal forces or vertical forces.|
|It is either a contact force or a non-contact force.||It possesses both contact and non-contact force.|
During the tug of war game, two forces act on the rope from both ends when two teams pull the rope. Suppose both teams apply the same amount of force to the rope, then the rope remains in the same position, and obviously, no team will win the game. Thus, one of the teams needs to apply a larger force than another team to switch the rope position towards them and succeed in the game.
Read more about Tension Force on the Rope.
Suppose team A is applying a force of 500 N on the rope and team B is applying a force of 300 N. Clearly, team A wins the game as it applies a larger force than team B.
That signifies if one force may be either action or reaction force larger than the other, it is called ‘unbalanced force’. If both forces have the same magnitude, they will balance or cancel each other. Hence, it is called ‘balanced force’. The unbalanced force could be either horizontal forces or vertical forces or both if they do not balance or cancel each other.
The net force is the sum of these unbalanced and balanced forces acting on an object.
In a box sliding on a floor example, if applied force 80N and friction force 60N, then the net force acting on the box is Fnet = 80 + (-60) = 20N. That means the box is accelerated when the net force of 20N is acting. Here, the applied force is an unbalanced force that changes the state of motion.
If friction force is bigger than applied force, i.e., 120N, then the net force on the box is Fnet = 80 + (-120) = -40N. That means the box is deaccelerating when the net force of -40 N is acting. Here, the friction force is an unbalanced force that changes the state of motion.
Suppose the friction force is the same as applied force, i.e., 80N, then the net force acting on the box is Fnet = 80 + (-80) = 0N. Since applied force and friction force have an equal magnitude, they cancel each other. Here, no net force acts on the box. Therefore, the box will not move.
Now we include the Vertical forces in this discussion.
On employing the push force on the box of 80N, the floor exerts the normal force of 60N, Gravity force of 60N, and friction force of 60N to the box. The net force is,
Fnet = (F1-F2) + (F3-F4)
Fnet = (80-60)+ (60-0)
Fnet = 20 N
That means the net force of 20N accelerates the box as forces are unbalanced.
But if the gravity force is 40N, then the net force is,
Fnet = (80-60)+ (60-40)
Fnet = 20-20
Fnet = 0
That means the net force is not accelerating the box as forces are balanced.
Read more about Gravitational Acceleration.
Net Force Vs Average Force
|Net Force||Average Force|
|We talk about the multiple forces acting on an object.||We talk about only a single force acting on an object.|
|It is a force applied by both stationary and moving objects.||It is a force applied by moving objects only.|
|It may act in all directions.||It acts in a single direction.|
|It includes both contact and non-contact forces.||It must be a contact force.|
|It does not include the time interval Δt in the formula.||It includes the time interval Δt in the formula.|
While playing cricket, when you hit a ball with a bat, a ball accelerates with increasing velocity. Not all the surface area of the ball is in contact with a bat; hence its applied force strength is different for different points in a ball surface. Therefore, the force exerted on a ball due to the moving bat, which is at a definite rate, is called the average force.
The ball’s velocity changes over a definite time after the average force applies. Hence, as Newton’s second law, the average speed is equivalent to the product of mass and rate of change of velocity.
More specifically saying, the average force varies the ball’s momentum P.
Since P = mv, where mass m remains constant when force applies.
The average force is also incorporated in the net force with all different forces which accelerate or deaccelerate an object.