Question

If a 5kg mass is raised to a height of 2cm .calculate the work done against the force of gravity (G=9.8ms-2

Answer 1

Answer:

Work against the gravity will be PE=mgh=5×10×10=500J

Total work done by the external force is W=Fd=170×10=1700J

so the kinetic energy gain will be KE=W−PE=1700J−500J=1200J

if the velocity becomes v then

2

1

mv

2

=1200Joule

or velocity v=

5

2400

=21.9m/s

Answer 2

Given :-

Mass of the object = 5 kg

Height of the object lifted = 2 cm

To Find :-

The work done by the body on mass.

Analysis :-

Here we are given with the mass and the height.

In order to find the work done substitute the given values from the questions accordingly such that work done is equal to mass into gravity into height.

Solution :-

We know that,

• m = Mass
• w = Work done
• g = Gravity
• h = Height

Using the formula,

$\underline{\boxed{\sf Potential \ energy=Mass \times Gravity \times Height}}$

Given that,

Mass (m) = 5 kg

Gravity (g) = 9.8 m/s

Height (h) = 2 m  = 0.02

Substituting their values,

⇒ w = mgh

⇒ w = 5 × 9.8 × 0.02

⇒ w = 0.98 J

Therefore, the work done by the boy on mass is 0.98 J.