The net external torque on a system of particles about an axis is zero. Which of the following are compatible with it?

Question

The net external torque on a system of particles about an axis is zero. Which of the following are compatible with it? (A) The forces may be acting radially from a point on the axis (B) The forces may be acting on the axis of rotation (C) The forces may be acting parallel to the axis of rotation (D) The torque caused by some forces may be equal and opposite to that caused by other forces

Tardigrade Admin · Accepted Answer

When net external torque on a system of particles about an axis is zero,
i.e.,

τ = r \times F = r F sin θ τ =

Zero, where

θ

is angle between

r

and

F, τ

is unit vector along

τ

, then all the four statements (a), (b), (c), (d) are compatible.

Q. The net external torque on a system of particles about an axis is zero. Which of the following are compatible with it?

The forces may be acting radially from a point on the axis

The forces may be acting on the axis of rotation

The forces may be acting parallel to the axis of rotation

The torque caused by some forces may be equal and opposite to that caused by other forces

When net external torque on a system of particles about an axis is zero, i.e., τ=r×F=rFsinθτ= Zero, where θ is angle between r and F,τ is unit vector along τ, then all the four statements (a), (b), (c), (d) are compatible.

When net external torque on a system of particles about an axis is zero,
i.e., $τ = r \times F = r F sin θ τ =$ Zero, where $θ$ is angle between $r$ and $F, τ$ is unit vector along $τ$ , then all the four statements (a), (b), (c), (d) are compatible.