Question

A string is used to pull a block of mass m vertically up by a distance h at a constant acceleration g/3 . The work done by the tension in the string is .

Answer 1

T= m( g+a)

=m ( g+g/3)

T= 4mg/3

workdone = Tension × Distance

= 4mg/3×h

= 4mgh/ 3

Answer 2

AnswEr :

Explanation :

From the Question,

• Mass of the Block = m

• Acceleration of the block = g/3

• Displacement : h

To finD

Work done by the string to vertically displace the block

Forces acting on the body :

• Tension

• Gravitational Force

Here,

The block is moving upwards with an acceleration (say a)

$\sf T > F_G \\ \\ \longrightarrow \sf T - F_G = F_{net} \\ \\ \longrightarrow \sf T = m(g + a)$

Work Done by the force would be :

$\sf W = T . h \\ \\ \longrightarrow \sf W = m(g + a)h \\ \\ \longrightarrow \sf W = m(g + \dfrac{g}{3})h \\ \\ \large{\longrightarrow \boxed{\boxed{\sf W = \dfrac{4}{3}mgh}}}$