Question

Q no : 7.An object of mass 20kg is raised to a height of 10 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half way down. g=10m/s​

Answer 1

Explanation:

given :

• object mass = 20 kg

• ground height = 10 m

• kinetic energy acceleration = g=10m/s

to find :

• potential energy and kinetic energy

solution :

first we will do potential energy :

• formula = potential energy = mass gravity height

m = mass of object

h = ground of height

g = Acceleration of gravity

then, we will start doing :

• potential energy = 20 × 10× 10

• potential energy = 2000

so , potential energy = 2000

then, we find kinetic energy :

formula :

• kinetic energy = mass gravity height

• kinetic energy = 20 × 10 × 5

• kinetic energy = 200 × 5

• kinetic energy = 1000

so , kinetic energy = 1000

Answer 2

Given :

• Mass of the body = 20kg
• Height it went upwards = 10m
• Acceleration (Here, gravity) = 10m/s²

To Find :

• Potential Energy of the body?
• Kinetic energy of the body?

Formula To Be Applied :

We will use the formula of potential Energy of a body :

• PE = m×g×h

Now, the formula of kinetic energy:

• KE = ½×m×v²

Solution :

Now, as Given:

Mass = 20 kg

Gravity ≈ 10m/s²

hieght = 10m

$\displaystyle \rm \implies pe = mgh$

$\displaystyle \rm \implies \: pe = 20 \times 10 \times 10$

$\blue{ \underline{ \boxed{ \displaystyle \rm \implies pe = 2000 \: j}}}$

Hence, Potential Energy = 2000 J

__________________________

Now, as we all know that the kinetic energy is calculated upon the final velocity of the object, so :

Acceleration (Gravity) =10m/s²

Displacement = 10

It is clearly observable that, the body will travel 10m in its first second,

So, final velocity while touching ground = 10m/s

Mass = 20kg

$\displaystyle \rm \implies ke = \frac{1}{2} \times m {v}^{2}$

$\displaystyle \rm \implies ke = \frac{1}{2} \times 20 \times 10 \times 10$

$\displaystyle \rm \implies ke = \frac{1}{2} \times 2000$

$\red{ \underline{ \boxed{ \displaystyle \rm \implies ke = 1000 \: j}}}$

So, Kinetic Energy = 1000 J