Question

certain force acting on a 2kg mass charges its velocity from 5m/s to 2m/s calculate work done by the force​

Answer 1

Given that,

• Initial Velocity,u = 5 m/s
• Final Velocity, v = 2 m/s
• Mass of the body, m = 2 Kg

To find : Work done by the retarding force.

According to Work Energy Theorem,

Work done by all the forces is equal to the change in Kinetic Energy.

W = ∆K

$\longrightarrow$ W = (Kinetic Energy)$\sf _{final}$ - (Kinetic Energy)$\sf _{initial}$

$\longrightarrow$ W = 1/2mv² - 1/2mu²

$\longrightarrow$ W = m/2(v² - u²)

$\longrightarrow$ W = 2/2(2² - 5²)

$\longrightarrow$ W = 4 - 25

$\longrightarrow$ W = -21 J

Work done by the retarding force is -21 J

Answer 2

Answer:

• Work done = -21 Joules

Explanation:

Given

• Mass of body, m = 2 kg
• Initial velocity of body, u = 5 m/s
• Final velocity of body, v = 2 m/s

To find

• Work done by force, W =?

Knowledge required

• Work energy theorem

According to the work-energy theorem, the net work done by the forces on a body is equal to the change in its kinetic energy.

       Work done = Final K.E. - Initial K.E.

Solution

By Work energy theorem

→ Work done = Final K.E. - Initital K.E.

→ W = 1/2 m v² - 1/2 m u²

→ W = 1/2 m ( v² - u² )

→ W = 1/2 ( 2 ) ( 2² - 5² )

→ W = 4 - 25

→ W = -21 J

Therefore,

• Work done by the force is 21 Joules in magnitude. and negative sign in W = -21 J represents that Force was acting opposite to the displacement of body.