Question

A stone of mass 6 kg is dropped from rest. What will be the kinetic energy of the block at the end of 5th second ?​

Answer 1

We have,

• Mass of stone(m) = 3 kg
• Intial velocity(u) = 0 {As it was dropped from rest}

We need to find the kinetic energy at 5th second,or simply after 5 seconds.

And the formula for kinetic energy is,

• K.E = ½ × m × v²

We have mass from the question & for v(final velocity) let us use 1st equation of motion;

• v = u + at
• v = 0 + 9.8 × 5 { a(9.8) because it is falling under the influence of gravity & t = 5 already mentioned in ques}
• v = 49 m/s

Now just put value of m & v in formula of K.E;

• K.E = ½ × 6 × (49)²
• K.E = 3 × 49 × 49
• K.E = 147 × 49
• K.E = 7203 J

Therefore,kinetic energy of the block at the end of 5th second will bs 7203 J.

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