1. What is not the condition for the equilibrium in three dimensional system of axis?
a) ∑Fx=0
b) ∑Fy=0
c) ∑Fz=0
d) ∑F≠0
Explanation: For the equilibrium in the three dimensional system of axis we have all the conditions true as, ∑Fx=0, ∑Fy=0 and ∑Fz=0. Also, we have the summation of the forces equal to zero. Which is not a non-zero value
2. We first make equilibrium equations and then the free body diagram and then solve the question.
a) True
b) False
Explanation: We first make the free body diagram and then we make the equilibrium equations to satisfy the given conditions. This helps us to solve the question easily. As this reduces the part of imagination and increases accuracy too.
3. ∑Fx=0, ∑Fy=0 and ∑Fz=0 are vector equations.
a) True
b) False
Explanation: The answer is false as the equations asked are scalars. As we make the net sum of the forces along the axis equal to zero. Of course this equation comes from the solving the vector forms, but still, the result is a scalar, hence the equations are scalar
4. When the body is in equilibrium then which of the following is true?
a) We equate all the components of the forces acting on the body equal to their resultant vector’s magnitude
b) We equate all the components of the forces acting on the body equal to their resultant vector’s magnitude square
c) We equate all the components of the forces acting on the body equal to their resultant vector’s magnitude square root
d) We equate all the components of the forces acting on the body equal to zero
Explanation: Yes, we equate all the components of the three axis equal to zero. That is the resultant of the forces along the three axis are being equated to zero. This brings in that there is no net force in any direction. Hence equilibrium
5. If solving the question in 3D calculations is difficult, then use the 2D system and then equate the total net force to zero.
a) True
b) False
Explanation: The answer is obviously yes. If we are having any difficulty in making the vector components, then we can go in 2D. As if the particle is in equilibrium, the net force will be zero. No matter where you see first. Net force is zero
6. If the resolved force or the force which you get as the answer after solving the question is negative, then what does this implies?
a) The force is in the reverse direction w.r.t the direction set in the free body diagram
b) The force is not in the reverse direction w.r.t the direction set in the free body diagram
c) The force component is not possible
d) The force is possible, but in the direction perpendicular to the resultant force
Explanation: The negative sign implies things in the opposite manner. If the force is coming negative this doesn’t mean that it is impossible. But it means that the force is in the opposite direction w.r.t the direction set by you in the free body diagram.
7. An electromagnet crane is carrying the electromagnet with the help of the three cables. But the electromagnet is not stable because of the wind. What is science behind the cause?
a) The wind is making the net force of the body equal to a non-zero value
b) The wind is making the net force of the body equal to zero value
c) The wind is making the net force of the body equal to a non-zero value but is supporting the equilibrium
d) The wind is making the net force of the body equal to zero value and supporting equilibrium
Explanation: Anybody is in equilibrium only if the net force along the three axis is zero. But in this case, the wind is not helping the body to do so. The science behind this is that the resultant forces are being equated to a non-zero value by the wind. Hence unstable.
8. If anybody is tied to three or more ropes, and then is allowed to achieve its equilibrium. Then the equilibrium achieved is achieved w.r.t what?
a) The three axis of the body
b) The ground
c) The ropes direction
d) The weight direction
Explanation: Yes, the equilibrium is being achieved w.r.t the ground. Like the motion, w.r.t ground need be zero. That is the relative velocity of the object or the body must be zero w.r.t the ground. This means motion is in equilibrium.
9. What does the moment of the force measure?
a) The tendency of rotation of the body along any axis
b) The moment of inertia of the body about any axis
c) The couple moment produced by the single force acting on the body
d) The total work is done on the body by the force
Explanation: The moment of the force measures the tendency of the rotation of the body along any axis, whether it be the centroid axis of the body or any of the outside axis. The couple moment is produced by two forces, not by a single force. The total work done is the dot product of force and distance not the cross.
10. If a car is moving forward, what is the direction of the moment of the moment caused by the rotation of the tires?
a) It is heading inwards, i.e. the direction is towards inside of the car
b) It is heading outwards, i.e. the direction is towards outside of the car
c) It is heading forward, i.e. the direction is towards the forward direction of the motion of the car
d) It is heading backward, i.e. the direction is towards the back side of the motion of the car
Explanation: When you curl your wrist in the direction in which the tires are moving then you will find that the thumb is pointing outwards. That is outwards the body of the car. This phenomenon is also observed in rainy seasons. When cars travel on the roads, the water is thrown outside from the tires, due to moment.