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What will be the effect on a rigid body if two like unequal parallel forces act on the body? Will the body translate or rotate or both? If they rotate, with respect to which point will they rotate?enter image description here

Here I have mentioned 'Like Unequal Parallel' forces, not 'Unlike Unequal Parallel' forces.

Kawsar Ahmed
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If the torque is non-zero the body will rotate and translate. However, if the torque is zero the body will only translate with an acceleration: $a=\frac{F_{1}+F_{2}}{m}$.

user154508
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  • If they rotate, with respect to which point will they rotate? – Kawsar Ahmed May 07 '17 at 08:22
  • @Hisab I am not sure but I think: If the the two forces are parallel $F_{1}r-F_{2}(L-r)=0$ where L is the lenght of the segment that connects the two points where the two forces act. – user154508 May 07 '17 at 09:17
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    Draw two lines. One touching the tails of both force vectors; the other touching the heads. The point where they meet is the ICR. – Abhijeet Melkani May 07 '17 at 15:56
  • I have drawn two lines as you said. But they don't meet. Have a look: http://tinypic.com/r/ohnzvl/9 – Kawsar Ahmed May 07 '17 at 16:39
  • Use this formula, $r=\frac{F_{2}L}{F_{1}+F_{2}}$ the distance r is calculate from the tail of $F_{1}$ and $L$ is the total lenght of the segment touching the tails of the forces – user154508 May 07 '17 at 17:03
  • You should extend those lines Hisab and they'll meet somewhere to the left(in your figure). As long as the forces are unequal the lines would always meet. – Abhijeet Melkani May 08 '17 at 08:00