Question

An 80-cm uniform 10-kg bar is resting on two scales, one at either end. A smaller 4-kg mass (m) is placed at a distance of d = 20 cm from the left end. Because the mass is closer to the left scale, it reads a higher weight than the right scale. What is the difference between the weights read by the two scales (left scale minus right scale)?

Answer 1

given,

length of bar = 80 cm

mass of the bar = 10 kg

smaller mass = 4 kg

distance = 20 cm

`s_1 + s_2 = 10 + 4`

`s_1 + s_2 = 14\ kg`

taking moment about B

`s_1 * 0.8 - 10 * 0.4 - 4 * 0.6 = 0`

`s_1 * 0.8 = 6.4`

`s_1 = 8\ N`

`s_2 = 14 - s_1`

`s_2 = 14 - 8`

`s_2 = 6 N`

difference between two scale = 8 - 6

= 2 N