Question

A 40 gram body starting from rest falls through vertical distance of 25cm before its types to the ground. then (given g=9.8 m/s square)A) kinetic energy of a body just before it hits the ground is 0.049JB) kinetic energy of the body just before it hits the ground is 0.098JC) velocity of the body just before it hits the ground 0.05m/sD) velocity of the body just before it hits the ground is 2.21m/s​

Answer 1

Answer:

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Explanation:

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Answer 2

Given: Mass of body = 0.04 kg

           Height through which body falls = 0.25 m

To Find: Kinetic energy of the body just before it falls to the ground

             Velocity of the body just before it falls to the ground

Solution:

PART (A)

• For solving this question we will apply the principle of conservation of mechanical energy which states that:

In an isolated system, the sum of conservative forces remains constant.

• By this principle we can infer that before beginning to fall the body had some potential energy(P.E) which gets completely converted to kinetic energy(K.E) just before it falls to the ground.

                 PE = mgh

where, m is mass of the body

           g is acceleration due to gravity

    and h is height

Substituting given values in formula for PE, we get

           PE = 0.04 kg × 9.8 m/$s^{2}$ × 0.25

                 = 0.098 J

This PE gets converted to KE by the end of the body's fall,

∴ Kinetic Energy of the body just before it hits the ground = 0.098 J  (1)

PART (B)

• For finding velocity of body just before it hits the ground, we will use the value of KE calculated in PART (A).

Formula for KE is given by:

    KE = $\frac{1}{2}$ m$v^{2}$

where v is the velocity of the body

Substituting given values into formula for KE,

          0.098 = $\frac{1}{2}$ × 0.04 × $v^{2}$ = 0.02 × $v^{2}$

⇒          $v^{2}$ = $\frac{0.098}{0.02}$

⇒         $v^{2}$ = 4.9

⇒         v = √4.9

⇒         v = 2.21 m/s

∴ Velocity of body just before it hits the ground = 2.21 m/s

Hence, Kinetic Energy of the body just before it hits the ground is 0.098 J and velocity of body just before it hits the ground is 2.21 m/s.