Equation for the tension in the string

  • Thread starter Thread starter Gughanath
  • Start date Start date
  • Tags Tags
    String Tension
AI Thread Summary
The discussion revolves around calculating the value of k in a pulley system with two masses, 3m and km, where A accelerates at 2/5g. The initial calculation yielded k as 1.29, but it was clarified that k must be greater than 3. Participants confirmed that if km is greater than 3m, A would accelerate upwards, leading to a revised calculation of k as 7. The importance of correctly interpreting the problem's conditions was emphasized, resulting in a clearer understanding of the relationship between the masses and acceleration. The final consensus is that k should indeed be greater than 3, confirming the revised value.
Gughanath
Messages
118
Reaction score
0
Two objects A and B hang down on either side of a smotth pulley, connected by an inextensible string. The masses of the objects are 3m and km respectivly. A accelerated at 2/5g when released. g=9.8N. What is the value of k.
I worked it out to be 1.29, by writing an equation for the tension in the string for both objects. But the the value of k is supposed to be greater than 3. :confused: Did I use the wrong method?
 
Physics news on Phys.org
What direction does A accelerate? You assumed down, and got the correct answer for that assumption. If km > 3m, then A would accelerate up. Try making that assumption and solve for k.
 
yes. This time round I get k=7? Is this right?
 
Oh right. I didnt read the question properly. if k is bigger than 3, then obviously its the greater mass. Thanks for clearing my problem.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Thread 'Struggle to understand the concept of the question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »

Similar threads

2 pullies and 3 masses -Tension
Replies
18
Views
4K
Tension in a string which connects 3 pulleys
Replies
12
Views
1K
Block and pulley on movable incline
Replies
2
Views
2K
Tension in 4 strings suspending object at 4 different points
Replies
19
Views
4K
Collisions, Impulses and Impulsive Tension
Replies
17
Views
4K
Equilibrium Tension Along a Curved String
Replies
3
Views
2K
Tension and frequency of a vibrating violin string
Replies
26
Views
7K
How is tension in a string affected by moment of inertia?
Replies
2
Views
4K
Tension from two carts & hanging object on pulley
Replies
7
Views
4K
Tension in a string in circular motion
Replies
15
Views
6K

Hot Threads

Recent Insights

Back
Top