Sandy asked in Science & MathematicsPhysics · 9 months ago

# Not sure how to do the Free Body Diagram for part (C)?

In a physics experiment on static friction, two objects made of identical material are tied together with a string. The first object has a mass of 5.0 kg and the second object has a mass of 3.0 kg. Students measure the maximum force of static friction as 31.4 N to move both objects across a horizontal surface.

(a) What is the coefficient of static friction?

(b) What is the magnitude of the tension in the string if they pull on the first object?

(c) A student pushes the 3.0 kg object with a force of 15.0 [down]. What are the magnitudes of the maximum force of static friction and the tension now?

(d) Will your answers to (c) change if the student pushes down on the 5.0 kg object instead? Explain.

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• Anonymous
9 months ago

In a physics experiment on static friction, two objects made of identical material are tied together with a string. The first object has a mass of 5.0 kg and the second object has a mass of 3.0 kg.

Students measure the maximum force of static friction as 31.4 N to move both objects across a horizontal surface.

(a) What is the coefficient μs of static friction?

μs = F/((m1+m2)*g) = 31.4/ ((5+3)*9.80) = 0.40

(b) What is the magnitude of the tension T in the string if they pull on the first object?

T = F*m2/(m1+m2) = 31.4*3/8 = 11.8 N

(c) A student pushes the 3.0 kg object with a force of F' = 15.0 [down]. What are the magnitudes of the maximum force of static friction and the tension T' now?

I guess F' = 15 N and drag at constant speed , therefore static friction increases by 15*0.4 = 6.0 N , as well as the tension T' that becomes equal to 17.8 N

(d) Will your answers to (c) change if the student pushes down on the 5.0 kg object instead?

extra friction remains the same (6.0 N) , but tension won't change and remains equal to 11.8 N as computed at point (b)

• Dylan
Lv 6
9 months ago

The student is pushing downward so the free body diagram will be the same.

Only difference is the weight force also has an extra 15 N cause of the student pushing down on the box.