Question

Which has greater kinetic energy: a tennis ball that has a mass of 0.3 kg travelling at 80 m/s, or a train that has a mass of 10000 kg and is moving at 0.1 m/s?

Answer 1

Solution :

• mass of tennis ball = 0.3 kg
• velocity of tennis ball = 80m/s
• mass of train = 10000kg
• velocity of train = 0.1m/s

Kinetic energy= 1/2 mv²

• Kinetic energy of tennis ball :

= 1/2 × 0.3 × 80²

= 1/2 × 0.3 × 80 × 80

= 0.3 × 40 × 80

= 0.3 × 3200

= 3/10 × 3200

= 960 Joules

• Kinetic energy of train :

= 1/2 mv²

= 1/2 × 10,000 × 0.1²

= 5000 × 0.1 × 0.1

= 5000 × 1/10 × 1/10

= 50 joules

Hence

• A tennis ball has much more kinetic energy then a train.

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