Question

Q.)The kinetic energy of an object of mass,m moving with a velocity of 5ms-1 is 25J . what will be its kinetic energy when its velocity is doubled ?
(class 9th)(Ch - Work and Energy) ​

Answer 1

Answer:

100 J

Explanation:

Expression for kinetic energy is

Ek = Mass of the object

V = velocity of the object = 5 m/s

Given:- kinetic energy, Ek = 25 J

If the velocity of the object is doubled then V = 5×2=10m/s

Therefore, it's Kinetic energy becomes 4 times it's original value because it is proportional to the square of the velocity.

hence, Kinetic energy (KE) = 25×4= 100 J

Answer 2

★Given:-

• Kinetic energy = 25J
• Velocity = 5m/s
• Mass = m

★To find:-

• Kinetic energy when mass is doubled.

★Solution:-

Using the formula,

✦K.E = 1/2 mv²

Substituting values,

➜K.E = 1/2 mv²

➜25 = 1/2 (m)(5)²

➜1 = 1/2 (m)

➜m = 2kg.

Therefore,mass of the object is 2kg.

Now,when its velocity is doubled,the new velocity will be '2v'.

Putting values in the formula,

➜K.E = 1/2 mv²

➜1/2 ×(2)(2v)²  

➜1/2 ×2×4v²

➜4v² =4(5)²

➜4×25 = 100J.

Therefore,the kinetic energy when velocity is doubled is 100J.

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