A person who prides her/himself on her/his common sense and her/his grasp of \"t

Question

A person who prides her/himself on her/his common sense and her/his grasp of "the real world" insists that defining a force is simple: "forces can cancel out, of course, but if an object is moving, then I know that a net (uncanceled) force must be acting on it; so that is how I recognize that a net force is acting on an object -- the object must be moving."

Discuss the accuracy and precision of this statement: can it be accepted without qualification? Use your own experience of moving objects to illustrate your answer.

Explanation / Answer

The statement the person makes is incorrect. We need to understand the concept of force. Force is a function of mass and acceleration. Not velocity.

Force=mass*acceleration

Elaborating :Let us look at Newton's 1st law closely.

If an object experiences no net force, then its velocity is constant: the object is either at rest (if its velocity is zero), or it moves in a straight line with constant speed (if its velocity is nonzero).[

So even if an object is moving,it does not necessarily mean that a force is acting on it. An object moving in a straight line at a constant velocity of2 m/sec is experiencing no net force as acceleration in this case is zero (because acceleration is rate of change velocity and a constant velocity means rate of change is 0 making the acceleration =0)

Since Force=mass * acceleration

Force= mass *0 (in this case) making Force=0.

So, to figure out whether an unbalanced force is acting on a body, we need to figure out whether the velocity is constant or variable. A constant velocity indicates zero acceleration.

It's important to note that for a velocity to be constant, speed and direction both need to be constant for a body. So if an object is moving at a constant speedof 2 m/sec on a circular path, the direction is changing which means there is a net acceleration acting on that object which indicates a non zero force on the body.

Conclusion: If a body has mass and has acceleration, then an unbalanced force is acting on the body.In all other cases, no unbalanced force would be acting on the body.

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