Sample 1Medium
A diagram shows a block of weight 100 N hanging from a knot O. Two light strings run from O to two hooks in the ceiling, one up to the left and one up to the right, each making 30° with the horizontal. The system is at rest. What is the tension in each string?
Show the answer
The answer is C.
Vertical balance at O: 2T sin 30° = 100 N, so T = 100 N. The horizontal components of the two tensions cancel.
- A.
50 N assumes each string carries half the weight vertically with no angle, i.e. strings vertical.
- B.
57.7 N uses cos 30° in place of sin 30°, which would be correct for angles of 30° with the vertical.
- D.
200 N doubles the correct value; 2T sin 30° = T, not T/2.
NCERT: Class 11 Physics, Chapter 4