# Math Help - Quick Physics torque question - Need a check

1. ## Quick Physics torque question - Need a check

So I've gotten an answer, but my percent error was huge, which is why I want to make sure that I did it right. Can someone do this real quick and tell me what they get?

[not drawn to scale]

Thanks!

2. net torque caused by the 10 gram mass ?

(.010)(9.8)(.48) = .047 N-m

I get x = 2.4 cm to balance the system using the 200 gram mass.

3. Thanks, that's what I got. I guess it's meant to have a huge percent error. What could be the cause of a 70% error? (the "actual" value should have been 8m with a 200 kg mass)

4. Originally Posted by Intrusion
So I've gotten an answer, but my percent error was huge, which is why I want to make sure that I did it right. Can someone do this real quick and tell me what they get?

[not drawn to scale]

Thanks!
$M_1 = F_1 \times d_1 = 0.48m \times 0.01(9.81) = 0.047Nm$

$\Sigma M = M_1+M_2 = 0.047-(x\times 0.2 \times 9.81) = 0$

Hence:

$x = \frac{0.047}{0.2\times 9.81} = 0.024m$

5. Since 200 is 10 x 20

It stands to reason that 48/20 = x

Thus 2.4 cm

EDIT ---------------------------------

I see it's already been answered, sorry for excessive posting.

6. Originally Posted by Intrusion
Thanks, that's what I got. I guess it's meant to have a huge percent error. What could be the cause of a 70% error? (the "actual" value should have been 8m with a 200 kg mass)
But it isn't a 200kg mass, it's a 200g mass. 8m is ridiculous compared to the tiny torque exerted by the 10g mass.

7. Originally Posted by Mush
But it isn't a 200kg mass, it's a 200g mass. 8m is ridiculous compared to the tiny torque exerted by the 10g mass.
Yeah, I meant a 200g mass, not kg.

8. Originally Posted by Intrusion
Yeah, I meant a 200g mass, not kg.
Even at that, 8m would produce far too much torque.

10g mass is placed 48cm away, to balance this a 200g mass would be a lot closer than 48cm... and as you know 8m is far from being closer than 48cm.

9. Alright, I'll have to enlighten my teacher then and let him know his "actual" answer is wrong. Thanks!