When you pedal a bicycle on a flat road, your muscles supply energy. Class 9

When you pedal a bicycle on a flat road, your muscles supply energy. Class 9

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Question 1.

When you pedal a bicycle on a flat road, your muscles supply energy. In what forms does this muscular energy appear as you ride? Class 9

Answer:

When pedalling on a flat road at constant speed, muscular (chemical) energy is converted into:

1. Kinetic energy of the bicycle and rider.
2. Thermal energy due to friction at the wheels, chain, and road surface.
3. Sound energy (small amounts).
4. Thermal energy of the surrounding air due to air resistance. On a flat road at constant speed, most energy goes to overcoming friction and air resistance, appearing primarily as thermal energy.

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Question 2.

Two objects A and B of mass m and 4 m have the same kinetic energy. What is the ratio of the magnitude of velocities of A and B? Class 9

Answer:

Kinetic energy = (1/2)mv²

Since both have same kinetic energy:

(1/2)m(v₁)² = (1/2)(4m )(v₂)²

=> m(v₁)² = 4m(v₂)²

=> (v₁)² = 4(v₂)²

=>v₁ = 2v₂

So, the ratio of velocities = v₁ : v₂ = 2 : 1