Solving Physics Problems: Tension, Friction, and Acceleration Explained

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The discussion centers on solving a physics problem involving two blocks connected by a string on a frictionless surface. The main questions include calculating the tension in the string and determining the new acceleration and tension if friction is introduced. It is clarified that the tension will be less than the applied force due to the combined acceleration of both masses. Participants emphasize understanding the forces acting on the system and suggest considering the blocks as a single system before analyzing them separately. Mastery of force calculations is highlighted as key to solving such problems effectively.
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Physics Problem. Please HELP!

Homework Statement


Two blocks on a frictionless horizontal surface are connected by a light strong. Gravity is 9.8.
Diagram:
4.13kg--T--21.2kg--->50.8N
a. What is the tension in the string between the blocks? Answer in units of N.
b. If the surface were frictional, and the coefficient of kinetic friction between each block and the surface is 0.0958, what would be the new acceleration? Answer in units of m/s^2

c. What would be the new tension in the string between the blocks? Answer in units of N




Homework Equations




The Attempt at a Solution


I thought that because it was frictionless for a. the tension would just be 50.8 again, but it was wrong...(im entering answers online)

grrr...I'm completely lost!

Help!? anyone?
 
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No, the tension between the two masses will be less. Just remember that F=ma, and both masses have the same acceleration. So there's a combination tension in the right string, and a single tension in the left string. Makes sense now?
 
Right; if the tension was somehow the same, then the force would be equal on both sides of the rightmost block and it would not move. Consider both masses as a single system first, then look at them separately. It took me a little while to get the hang of force calculations but once I really understood them it's easy as pie.
 
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}...
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