Question

A ball or mass 2oog has a kinetic energy of 20 J . calculate the speed of the movingball

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Answer 1

10√2 m/s is the required answer.

GIVEN:

• Mass of the ball , m = 200 g
• Kinetic energy, k = 20 J

TO FIND:

Speed of moving ball, v

FORMULA:

Kinetic energy, k = mv²/2

SOLUTION:

STEP 1: TO CONVERT MASS IN STANDARD UNITS

• SI unit of mass is kilogram, kg
• 1 gram = 10^-3 kg.
• 200 g = 200 × 10^-3 kg = 2 × 10² × 10^-3 kg
• Mass, m = 2 × 10^-1 kg.

STEP 2: TO FIND SPEED

$k = \frac{1}{2} m {v}^{2} \\ \\ 20= \frac{1}{2} \times 2 \times {10}^{ - 1} \times {v}^{2} \\ \\ 20 = {10}^{ - 1} \times {v}^{2} \\ \\ {v}^{2} = \dfrac{20}{ {10}^{ - 1} } \\ \\ {v}^{2} = 20 \times {10}^{1} \\ \\ {v}^{2} = 2 \times 100 \\ \\ v = \sqrt{2 \times 100} \\ \\ v = \sqrt{2} \times \sqrt{100} \\ \\ v = \sqrt{2} \times 10 \\ \\ v = 10 \sqrt{2 } \: \frac{m}{s}$

ANSWER:

Speed of the moving ball is 10√2 m/s.

KINETIC ENERGY:

• Energy is the capacity to do work.

• Kinetic energy is the energy possesed by the body by virtue of its motion.

• It is a scalar quantity.

• It is directly proportional to the dot or scalar product of velocity vector.

• Kinetic energy depends on the mass of the body in motion.

Answer 2

Answer:

10√2 m/s

Explanation:

First convert 200 g to kg.

=> 200 g => 200/1000 => 0.2 kg

Kinetic energy formula = 1/2mv²

=> 20 = 1/2*0.2*v²

=> 20 = 0.1v²

∴ v² = 20/0.1 => 200

∴ v = √200 => 10√2 m/s