# Torque for axle

1. Jun 13, 2015

### siva surya

when 10 cm rope pull axle and wheel and in which axle is 10 cm in diameter and wheel is 100 cm in diameter in which wheel hangs a weight 10 kg of metal ..in this how to much torque is required to rotate axle?

2. Jun 13, 2015

### billy_joule

Could you draw a diagram? Or rephrase your question? I can't understand the question.

It may be that:
T = Fr where the force is due to the 10kg mass and r is the radius of the axle?

3. Jun 14, 2015

### siva surya

in this
1.how much torque is reuired to rotate axle of diameter 10 cm
2.and on the other end wheel is attached of diameter 100 cm and hang with 10 kg of weight
3.then in how many kg should be axle and wheel metal ?

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• ###### dia fr phy frm.png
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4. Jun 14, 2015

### billy_joule

1. It depends on how fast you want the system to accelerate.
T = Iα
Where T is torque, I is moment of inertia and α is angular acceleration.

The moment of inertia depends on geometry and mass:
https://en.wikipedia.org/wiki/Moment_of_inertia

The above only considers the torque required to accelerate the axle & pulley, additional torque will be required to accelerate the hanging mass upwards.

3. The mass of the axle & wheel will be the volume multiplied by density. The required geometry will depend on the forces applied, in other words it needs to be of a certain size (and mass) so it doesn't break.

Is this homework? Or a real project? Maybe you are trying to design a hand winch?

5. Jun 14, 2015

### siva surya

i like to design no energy machine

6. Jun 14, 2015

### billy_joule

7. Jun 14, 2015

### siva surya

ya like to use gravity as energy

8. Jun 14, 2015

### CWatters

Gravity is not considered a source of energy (but you can use gravity to store energy from another source).

The torque must be at least..

= (10Kg * 9.81) * 100/10
= 981 Nm

That torque will stop the weight falling. If you want to raise the weight then (as billy said) you need to tell us how fast you want it to accelerate and the moment of inertia of the pulleys etc. Friction?

9. Jun 14, 2015

### siva surya

if the 10 kg mass falls as free fall and create impact force means whats the impact force on there
in which mass 10 kg
height 20 cm
whats newton there

Last edited by a moderator: Jun 14, 2015
10. Jun 15, 2015

### CWatters

The impact force depends on what the 10kg mass is made of and what it hits. One way to visualise this is that it will be higher for concrete than carpet because the "stopping distance" is shorter.

If you assume it hits something like modelling clay and has constant deceleration you can estimate using..

V2 = U2 +2as

where
U2 = velocity at impact
V2 = velocity after impact, probably zero
a = acceleration
s = distance (eg depth of impact crater)

So you could measure the depth of the impact crater and plug in the numbers to estimate the deceleration "a".

Then use F = ma to estimate the implied impact force.

The results will be very approximate. In the real world it's better to attach an accelerometer to the mass and measure "a".

11. Jun 15, 2015

### siva surya

how much torque is required to pull up to weight 11 kg from 100 cm through wheel and axle?

12. Jun 15, 2015

### siva surya

how much torque is required to pull up to weight 11 kg from 100 cm through wheel and axle?

13. Jun 15, 2015

### TESL@

110 Nm

14. Jun 16, 2015

### CWatters

In post #8 I showed you how to calculate the torque for 10kg...

For 11kg the sum becomes..
= (11Kg * 9.81) * 100/10
= 1079 Nm