Net torque question? Block 1 and block 2 hanging on pulley?

In summary, the problem at hand involves a pulley with a horizontal axle and negligible friction, with a radius of 5.0cm. Block 1 has a mass of 460g and block 2 has a mass of 500g. When released from rest, block 2 falls 75.0cm in 5.00s without the cord slipping on the pulley. The rotational inertia is being asked for in part (e) of the problem, which can be solved using the equation Ʃτ = (T2 - T1)R. The masses mg1 and mg2 will be taken into account in later steps, as the pulley only feels the tension from the strings. It is important to
  • #1
nchin
172
0
In Fig. 10.45, block 1 has mass m1=460g, block 2 has mass m2=500g, and the
pulley, which is mounted on a horizontal axle with negligible friction ahs radius
R=5.0cm. When released from rest, block 2 falls 75.0cm in 5.00 s without the
cord slipping on the pulley.

(e) What is its rotational inertia?

problem and picture on page 2 problem #55

http://faculty.kfupm.edu.sa/PHYS/marzoug/Phys101/chapter 10 problmes.pdf




Ʃτ = (T2 - T1) R

Why doesn't mg1 or mg2 get calculated into the net torque and only the tensions?



thanks!
 
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  • #2
Why doesn't mg1 or mg2 get calculated into the net torque and only the tensions?
That happens later - there are three free-body diagrams.
It's good discipline for more complicated problems: the pulley knows nothing about the masses - all it feels is these strings pulling on it.
Note - the 1 and the 2 belong on the "m"'s not the "g"'s ... g is a constant.
 
  • #3
Simon Bridge said:
That happens later - there are three free-body diagrams.
It's good discipline for more complicated problems: the pulley knows nothing about the masses - all it feels is these strings pulling on it.
Note - the 1 and the 2 belong on the "m"'s not the "g"'s ... g is a constant.

thanks!
 

FAQ: Net torque question? Block 1 and block 2 hanging on pulley?

1. What is net torque?

Net torque is the sum of all the individual torques acting on an object. It is a measure of the rotational force that can cause an object to change its rotational motion.

2. How is net torque calculated?

Net torque is calculated by multiplying the force applied to an object by the distance between the force and the pivot point. This is represented by the equation T = F x r, where T is the torque, F is the force, and r is the distance.

3. What is a pulley?

A pulley is a simple machine that consists of a grooved wheel and a rope or cable. It is used to change the direction of a force, making it easier to lift or move heavy objects.

4. How does a pulley affect net torque in a block and pulley system?

In a block and pulley system, a pulley can change the direction of the force acting on the blocks, but it does not change the amount of force. This means that the net torque acting on the system is the same as the torque applied by the weight of the blocks.

5. How does the hanging position of the blocks affect net torque?

The hanging position of the blocks can affect net torque by changing the distance between the force applied by the weight and the pivot point. The further the blocks are from the pivot point, the greater the net torque will be.

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