| 1. |
the sum of two forces at a point 16 N. if the resultant is normal to the smaller force have value 8 N. find two forces. |
Answer» Answer:The forces are 6 N and 10 N Explanation:given that, the sum of two forces at a point is 16 N let the two forces be A and B so, here given, A + B = 16 .....(1) also given that, the resultant is normal to the smaller force have value 8 N, so, here, sum of vectors = 8 N i.e A^--> + B^-> = 8 N so, Resultant(R) of forces = 8 N now, ACCORDING TO THE FIGURE R² = A² + B² + 2(AB)cosθ putting the values, 8² = A² + B² + 2AB cosθ 64 = A² + B² + 2AB cosθ ...(2) now, by the direction formulae tanα = Bsinθ/(A + Bcosθ) here, α = 90 [according to the figure] putting the values, tan 90 = Bsinθ/(A + Bcosθ) ж = Bsinθ/(A + Bcosθ) ж = INFINITY so, A + Bcosθ = 0 Bcosθ = -A putting the value of Bcosθ on (2) 64 = A² + B² + 2ABcosθ 64 = A² + B² + 2A(-A) 64 = A² + B² - 2A² 64 = B² - A² 64 = (B + A) (B - A) from (1) B + A = 16 putting the value 64 = (B + A) (B - A) 64 = 16(B - A) B - A = 64/16 B - A = 4. ..(3) now, we have B + A = 16 ..(1) B - A = 4 ...(2) adding both equation, B + A + B - A = 16 + 4 2B = 20 B = 20/2 B = 10 now, putting the value of B on (2) B - A = 4 10 - A = 4 -A = 4 - 10 -A = -6 A = 6 so, ________________The forces are6 N and 10 N_______________now, for finding the angles between the forces 64 = A² + B² + 2ABcosθ putting the values 64 = 6² + 10² + 2(6)(10) cosθ 64 = 36 + 100 + 120 cos θ 120cosθ + 136 = 64 120cosθ = 64 - 136 120cosθ = 72 cos θ = 72/120 cos θ = 3/5 so, θ = 37 °Angle between the forces = 37° |
|