Question

Q41: A body of mass 5 kg initially at rest is subjected to a force of 20 N
Find the kinetic energy acquired by the body at the end of 10 sec.

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Answer 1

Answer:

Explanation:

Given :

• Mass of a body (m) = 5kg
• Force (F) = 20N
• Time (t) = 10 sec
• Initial velocity (u) = 0 m/s

To Find :

• The kinetic energy acquired by the body at the end of 10 sec.

Formula to be used :

• Newton's 2nd law of motion, ie,, F = ma
• 1st eqn. of motion, ie,, v = u + at
• Kinetic energy formula, ie,, K.E = ¹/2 × mv²

Solution :

★ Acceleration of a body,

According to the Newton's 2nd law of motion,

F = ma

⇒ 20 = 5 × a

⇒ a = 20/5

⇒ a = 4 m/s²

★ Final velocity of a body,

Applying 1st eqn. of motion,

v = u + at

⇒v = 0 + 4 × 10

⇒ v = 40 m/s

★ Kinetic energy acquired by a body,

Applying kinetic energy formula,

K.E = ¹/2 × mv²

⇒ K.E = ¹/2 × 5 × (40)²

⇒ K.E = 0.5 × 5 × 1600

⇒ K.E = 2.5 × 1600

⇒ K.E = 4000 J

Hence,

The kinetic energy acquired by the body at the end of 10 sec is 4000 J.