Need help with a centripetal force question

[sens]

Homework Statement

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Homework Equations

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mv^2 / r = F

The Attempt at a Solution

This is my attempt and reasoning for this problem, is this the correct way to approach the problem or am i missing something?the hanging mass is motionless the tension in string equals the force of gravity on mass m2, therefore
T = 4*9.8N
The horizontal force on the puck (which is the centripetal force) is the same as the tension.
F(horizontal) = 4*9.8 N
(c) mv^2 / r = F(centripetal) ===> (0.8)(v^2) / (1.5) = 4*9.8 ===> v = 8.57321 m/s

 

[gneill]

Your logic and method look good. You'll want to display the end result with the correct number of significant figures though.

 

[sens]

Your logic and method look good. You'll want to display the end result with the correct number of significant figures though.

Are you sure the answer is correct? The solution key that the professor just posted said the answer was 10.5 m/s so I'm trying to figure out where i went wrong.

 

[gneill]

I don't see any problem with your solution. Your result is correct for the problem given.

You might make your answer 10 m/s if you were rounding to one significant digit, but your professor's result has three. So that won't account for the difference.

 

[sens]

ok thank you for your help