Question

The forces, which meet at one point but their lines of action do not lie in one plane, are called:
A. Non-coplanar non-concurrent forces
B. Non-coplanar concurrent forces
C. Coplanar concurrent forces
D. Coplanar non-concurrent forces

Answer 1

The force is a vector quantity. If the two vectors lie on the same plane, then, they are called the coplanar vectors. If the vectors meet, then, they are called
the concurrent vectors. Using these properties of the vectors, we will find the answer.

Complete answer:
From the given information, we have the data as follows.
The forces meet at one point but their lines of action do not lie in one plane.
If the two vectors lie on the same plane, then, they are called the coplanar vectors. If the vectors meet, then, they are called the concurrent vectors.
The force is a vector quantity.
As the forces meet at one point. Thus, these forces can be called concurrent. The lines of actions of these forces do not lie in one plane, thus, these forces can be called non-coplanar.
A. non-coplanar non-concurrent forces – forces that do not lie in one plane and do not meet at one point.
B. non-coplanar concurrent forces – forces that do not lie in one plane and meet at one point.
C. coplanar concurrent forces – forces that lie in one plane and meet at one point.
D. coplanar non-concurrent forces – forces that lie in one plane and do not meet at one point.
$\therefore$ The forces, which meet at one point but their lines of action do not lie in one plane, are called non-coplanar concurrent forces.

Thus, option (B) is correct.

Note:
Other types of vectors: Collinear or parallel vectors – if the vectors lie on the same line, then, the vectors are said to be collinear, Co-initial vectors – if the vectors exist from the same initial point and different terminal point, then, the vectors are said to be co-initial, Coterminal vectors – if the vectors exist from the different initial point and terminate at the same point, then, the vectors are said to be coterminal.