Question 234: Laws of Motion

Question

Three blocks with masses m, 2m and 3m are connected by strings, as shown in the figure. After an upward force F is applied on block m, the masses move upwards at constant speed v. What is the net force on the block of mass 2m ? (g is the acceleration due to gravity)

Accepted Answer

From figure
F = 6 mg,
As speed is constant, acceleration a = 0
$$ 	herefore $$ 6 mg = 6ma = 0, F = 6 mg
$$ 	herefore $$ T = 5 mg , T' = 3 mg
T'' = 0
F
net
on block of mass 2 m
= T Ã¢ÂÂ T' Ã¢ÂÂ 2 mg = 0
ALTERNATE :
$$ \because $$ v = constant
so, a = 0, Hence, F
net
= ma = 0

Answer

3mg

Answer

6mg

Answer

zero

Answer

2mg

Laws of Motion

Three blocks with masses m, 2m and 3m are connected by strings, as shown in the figure. After an upward force F is applied on block m, the masses move upwards at constant speed v. What is the net force on the block of mass 2m ? (g is the acceleration due to gravity)

Choose the correct answer: