Equilibrium: What Must Be True?

[badboyben03]

if an object is in equilibrium, then which of the following must be true?

(i know net force has to be 0, forces are balanced, and acceleration is 0. it doesn't always mean it is at rest. i think there's still one or two more "must be trues" in the list.)

a. all individual forces acting upon the object are equal in magnitude.

b. the net force is 0 N.

c. the force of gravity is equal to the normal force.

d. the forces are balanced.

e. the acceleration is 0 m/s/s

f. the object is at rest

g. the velocity (whether zero or non-zero) is constant.

h. the velocity is changing.

 

[dimava]

I think A, C, D, G are also true, but I might be wrong

A) if they weren't equal, they wouldn't be in equilbrium

C) is the force of gravity wasn't equal to the normal force, it would fall

G) The velocity has to be either consitant or changing, and its not changing

 

[Doc Al]

Originally posted by dimava
A) if they weren't equal, they wouldn't be in equilbrium

A is not true. The forces can be different in magnitude, as long as the vector sum is zero. (Think about three forces acting on the body.)

C) is the force of gravity wasn't equal to the normal force, it would fall

C is not true. There might not even be a normal force. But if there was one, it may not equal the weight. (Consider a ladder leaning against a wall: does the normal force equal the ladder's weight?)