Question

Three forces of 30 gms, 50 gms and 60 gms respectively act an angle of 120 degrees from each other. Find the resultant by rectangular-resolution (a)by making the 30-gm force lie on the axis. (b) by making the 60-gm force lie on the x-axis.

Answer 1

have you computed it too? @Vincent-Lyon.Fr ?
i'm not sure, but is the resultant 55.68?

Answer 2

Before helping out with the calculation, let me make the following remark.

Although it is not your fault, note that 'gms' in neither a valid symbol for mass nor force.

symbol for gramme is 'g' :
- no plural
- no full stop; this is not an abbreviation but the the symbol of a mass-unit with a full mathematical value.

It is not correct either to write:
'the 60-g mass'

there should be no hyphen between 60 and g as '60 g' is in itself a quantity, in which 60 and g are factors in a multiplication.

Reference is: point 5.3.3 of English SI-Brochure of BIPM
http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf

Answer 3

ok..so the forces be 30 g, 50 g, and 60g...

Answer 4

Resultant should be: F = \(\sqrt {700}\) gf = 26.46 gf *

Fx = 30.cos0 + 50.cos120° + 60.cos240°
Fy = 30.sin0 + 50.sin120° + 60.sin240°

F = \(\sqrt{F_x^2+F_y^2}\)

*gram-force (symbol gf) is outside the SI, but is nevertheless a valid unit of force.

Answer 5

do you use rectangular resolution?

Answer 6

I don't know what you mean by that, but I resolve each vector in the plane according to its orientation.