Solving Physics Problems: Tension, Friction, and Acceleration Explained

[Landstander182]

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?

 

[berkeman]

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?

 

[gabee]

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.