Question

Three blocks with masses m, 2m and 3m are
connected by string, as shown in the figure
After an upward force F is applied on block
m, the masses move upward at constant
speed v. What is the net force on the block
of mass 2m? (g is the acceleration due to
gravity)
791
2mg
3mg
6mg
zero​

Answer 1

First mass = m

Given that,

Third mass = 3m

Second mass = 2m

Constant speed = v

Force = f

The masses move upward at constant speed v.

Constant speed means,

\dfrac{dv}{dt}=0

We know that,

Acceleration is equal to the rate of velocity of block.

a=\dfrac{dv}{dt}

Here, constant speed v =0

So,

a=0

Net acceleration is zero.

Net acceleration is zero then net force will be zero.

We need to calculate the net force on the block of mass 2 m

Using formula of force

F=ma

Where, F = net force

a = net acceleration

m = mass

Put the value into the formula

F=2m\times0

F=0

Hence, The net force on the block of mass 2 m is zero.

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Topic : Constant speed

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