Physics Balancing Forces

O Question 17 (Cod. : Simu4515_e)
Subject: LOGIC
A metal bar 1 metre long is suspended by its centre. At 10 cm from the right end hangs a 10 kg weight, while at the other end hangs a 36 kg weight. What must you do to balance the bar and keep it in the horizontal?
A: Add to the weight hung on the right end another weight of 35 kg
B: Nothing, the bar is already balanced
C: Add to the weight hung on the left end another weight of 28 kg
D: Add to the weight hung on the left end another weight of 35 kg E: Add to the weight hung on the right end another weight of 28 kg

This transcription was added by Ari Horesh from EnterMedSchool to provide accessibility for those with disabilities. Please note that the text may contain inaccuracies or errors and may not fully reflect the context or meaning of the original forum post.

Hi!

  • the pivot is at the center of the beam so we can ignore the moment of the beam
  • the 36 kg weight is at the very end of the left side of the beam, so 50cm from the pivot
  • sum of clockwise moments = sun of counter clockwise moments

counter clockwise: moment = 36 * 10 * 50 = 18000
clockwise: moment = Fd = mgd = 10 * 10 * 40 = 4000

40 * 10 * (10 + X kg) = 18000 for the beam to balance
35 = X

we must add 35 kg to the weight hung on the right to balance

Hope this helps!

1 Like

Thanks Juliette - super clear and easy to understand now

1 Like