Answer:
All are correct.
Explanation:
The equilibrium of an object occurs when:
1. The net force on the object is zero: When the number of forces acting on an object and the sum of all the forces is zero, then we say that the net force acting on the object is zero. It means that the net acceleration of the object is zero, it means the object is at rest or moving with constant velocity.
2. All forces acting on an object are balanced: When a number of forces acting on the object and the net force is zero it means all the forces are balanced. So, that the object has either zero velocity or moving with constant velocity.
3. The sum of +X forces on an object equals the sum of the - x forces: As the forces in + X axis direction is equal to the forces in - X axis direction, it means again the net force on the object is zero.
4. The sum of upward forces equal to the sum of downward forces: As the sum of forces in upwards direction is equal to the sum of forces in downward direction, it means the net force on the object is zero..
