Is it correct to say that no force acts on a body at rest?
A.) No force acts on a body at rest; if at least one force acted on it the body would move.
B.) No net force acts on a body at rest; when the net force is zero, the body is in static equilibrium
C.) No force acts on a body at rest; all forces cancel each other
D.) No net force acts on a body at rest; no force acts on the body at all
E.) All are wrong.
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The correct answer here is B. To understand why, think about anything that's stationary right now, for example the screen on your computer. You know that it cannot be true that no force is acting on it. After all, every object on Earth is being acted on by gravity at every moment.
So how come some objects don't move if gravity is acting on them? It's because there are other forces that cancel out the force of gravity. In this case, it's something called the "normal force" which is the term for the force that opposes gravity.
There are forces acting on a body at rest in all situations except theoretical ones. For example, a motionless bowling ball sitting on the floor has a gravitational force acting upon it. In fact, that is what keeps it motionless.
The bowling ball also exerts a gravitational pull on the earth. The net force acting upon the ball is zero, which puts the ball in static equilibrium, or more accurately, mechnical equilibrium.
It would be B.
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