Question

A dynamometer D is attached to two blocks of masses $6$ kg and $4$ kg as shown in the figure. The reading of the dynamometer is?

• A. $18$N
• B. $28$N
• C. $38$N
• D. $48$N

Answer 1

The correct option is C $38$N

Let x be the force recorded by dynamometer.

Both masses move in one direction.

The largest force is 50 N and the least is 30 N.

This means x lies between 50 and 30.

This can be represented as shown.

30 < x < 50

The resultant force on :

6 kg mass = 50 - x

4 kg mass = x - 30

They have equal acceleration as shown :

$\frac{(50-x)}{6}=\frac{(x-30)}{4}200-x=6x-180x=38\text{N}$