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Q1. As an object falls, its potential energy:
As an object falls, its height decreases. Since gravitational potential energy = mgh, potential energy decreases as height decreases. This energy is converted into kinetic energy.
Q2. In the formula mgh, ‘h’ represents:
In the formula for gravitational potential energy Ep = mgh, ‘h’ represents the height of the object above the reference level (usually the ground).
Q3. Air resistance is ignored in free fall to:
Air resistance is ignored in free fall calculations to simplify the analysis. In reality, air resistance affects falling objects, but ignoring it makes the calculations easier and follows the ideal free fall model.
Q4. Energy transformation is essential because:
Energy transformation is essential because all life processes depend on energy conversions. From photosynthesis in plants to cellular respiration in animals, life requires constant energy transformation.
Q5. Potential energy depends on:
Potential energy depends on the reference level chosen because it is measured relative to a reference point. Changing the reference level changes the value of potential energy.
Q6. A raised object can do work because it has:
A raised object has gravitational potential energy. This stored energy can be converted into kinetic energy, allowing the object to do work when it falls.
Q7. Total mechanical energy is the sum of:
Mechanical energy is the sum of kinetic energy (energy due to motion) and potential energy (energy due to position or configuration).
Q8. Energy conversion examples are found:
Energy conversion occurs everywhere – in nature (sunlight to food, falling water) and in daily life (electricity to light, fuel to motion). It is a universal phenomenon.
Q9. The potential energy gained by an object raised through height h is:
Gravitational potential energy gained = mgh, where m is mass, g is acceleration due to gravity, and h is the height through which the object is raised.
Q10. Gravitational potential energy is defined as:
Gravitational potential energy is the energy stored in an object when work is done against gravity to raise it to a certain height. It equals the work done = mgh.
Q11. If energy could not transform, then:
Life depends on energy transformations. Plants convert sunlight to chemical energy, animals convert food to energy. Without energy transformation, life processes would stop.
Q12. Raising an object along different paths to the same height requires:
Work done against gravity depends only on the vertical height, not on the path taken. Since work = mgh, the same height means the same work regardless of path.
Q13. If an object is raised to a greater height, its potential energy:
Potential energy = mgh. If height increases, potential energy increases proportionally. More height means more stored energy.
Q14. The formula for gravitational potential energy is:
Gravitational potential energy = mgh, where m is mass, g is acceleration due to gravity, and h is the height above the reference level.
Q15. A 10 kg object at a height of 6 m has potential energy:
Using Ep = mgh = 10 × 9.8 × 6 = 588 J (taking g = 9.8 m/s²). Note: 10 × 10 × 6 = 600 J if g = 10 m/s² is used.
Q16. If potential energy of an object is known, its height can be found using:
From Ep = mgh, height h = Ep/(mg). So if potential energy is known, height can be calculated using this formula.
Q17. The work done in lifting an object is stored as:
When an object is lifted, the work done against gravity is stored as gravitational potential energy. This energy can be released when the object falls.
Q18. When the arrow is released from the bow, the stored energy changes into:
The bow stores elastic potential energy when stretched. When released, this stored energy is converted into kinetic energy of the arrow, making it move.
Q19. When an object falls freely, its mechanical energy:
In free fall (ignoring air resistance), mechanical energy (sum of kinetic and potential energy) remains constant. As potential energy decreases, kinetic energy increases equally.
Q20. During free fall, the sum of potential and kinetic energy:
According to the law of conservation of energy, the sum of potential and kinetic energy (mechanical energy) remains constant during free fall in the absence of air resistance.
Q21. Stretching the bow stores energy in the bow as:
Stretching a bow stores elastic potential energy in it. This energy is released when the string is released, converting to kinetic energy of the arrow.
Q22. In free fall, potential energy changes into:
In free fall, gravitational potential energy is continuously converted into kinetic energy as the object falls and gains speed.
Q23. The law of conservation of energy states that energy:
The law of conservation of energy states that energy can neither be created nor destroyed. It can only be transformed from one form to another or transferred from one object to another.
Q24. The equation representing conservation of mechanical energy is:
This equation represents conservation of mechanical energy: Potential energy (mgh) + Kinetic energy (½mv²) = constant, assuming no energy loss.
Q25. Mechanical energy of an object is:
Mechanical energy is defined as the sum of an object’s kinetic energy and potential energy. ME = KE + PE.
Q26. Green plants get their energy mainly from:
Green plants get their energy from the Sun through photosynthesis. Sunlight is converted into chemical energy stored in food.
Q27. Work done by gravity depends on:
Work done by gravity depends only on the vertical height difference (mgh), not on the path taken. This is because gravity is a conservative force.
Q28. Energy transformation in falling objects is:
In falling objects, potential energy is converted into kinetic energy. As the object falls, its potential energy decreases and kinetic energy increases.
Q29. Energy transformation means:
Energy transformation means converting energy from one form to another, such as potential to kinetic, chemical to thermal, etc. Energy is neither created nor destroyed.
Q30. As an object falls, its kinetic energy:
As an object falls, it gains speed. Since kinetic energy = ½mv², kinetic energy increases as the object falls.
Q31. An object can have different potential energy values depending on:
Potential energy is measured relative to a reference level. Changing the reference level changes the potential energy value, even though the physical situation is the same.
Q32. At ground level, the potential energy of a falling object is:
At ground level, height h = 0, so potential energy mgh = 0. This is the minimum potential energy (taking ground as reference).
Q33. The ability of an object to do work depends on its:
Energy is defined as the capacity to do work. The more energy an object has, the more work it can do.
Q34. Mechanical energy remains constant when:
Mechanical energy remains constant when energy transformations occur without any loss (no friction or air resistance). This is ideal conservation of mechanical energy.
Q35. Just before hitting the ground, a falling object has:
Just before hitting the ground, the falling object has its maximum speed, so it has maximum kinetic energy. Its potential energy is minimum (zero at ground level).
Q36. Fuels like coal and petroleum store:
Coal, petroleum, and other fossil fuels store chemical energy in their chemical bonds. This energy is released when they are burned.
Q37. Potential energy is associated with:
Potential energy is stored energy due to an object’s position (gravitational) or configuration (elastic). It is not associated with motion.
Q38. At the top of its fall, a freely falling object has:
At the top of its fall, the object is at its maximum height, so it has maximum potential energy. It has zero kinetic energy because it starts from rest.
Q39. The energy gained by an object raised to a height is called:
The energy gained by an object when raised to a height is gravitational potential energy. It is stored energy due to position in a gravitational field.
Q40. Energy can be converted:
Energy can be converted from one form to another – potential to kinetic, chemical to thermal, electrical to mechanical, etc. This is a fundamental principle of physics.
Q41. The minimum force required to lift an object is equal to:
The minimum force required to lift an object is equal to its weight (mg). This force must balance the downward gravitational force.
Q42. An object of mass 12 kg has potential energy 480 J. Its height is:
Using Ep = mgh, h = Ep/(mg) = 480/(12 × 10) = 480/120 = 4 m (taking g = 10 m/s²). With g = 9.8, h = 480/(117.6) ≈ 4.08 m.
Q43. A system obeying conservation of energy shows that energy:
A system obeying conservation of energy shows that energy is transformed from one form to another, but the total energy remains constant.
Q44. Conversion of energy does not change:
The law of conservation of energy states that total energy remains constant during energy conversion. Only the form of energy changes.
Q45. The law of conservation of energy is valid:
The law of conservation of energy is a universal law. It is valid in all situations, from microscopic particles to macroscopic objects and across all physical phenomena.
Q46. At the start of free fall, the kinetic energy of the object is zero because:
At the start of free fall, the object is at rest, so its velocity is zero. Since kinetic energy = ½mv², it has zero kinetic energy.
Q47. Energy conversion occurs in:
Energy conversion occurs everywhere – in natural processes (photosynthesis, water cycle) and in human activities (using electricity, driving cars). It is a fundamental aspect of the universe.
Q48. According to the law of conservation of energy, total energy:
The law of conservation of energy states that the total energy of an isolated system remains constant. Energy can be transformed but the total amount is conserved.
Q49. An object gains energy when it is raised because:
When an object is raised, work is done against gravity. This work is stored as potential energy, so the object gains energy.
Q50. The energy stored in a stretched bow is due to:
A stretched bow has elastic potential energy due to its change in shape. This is stored energy that can be converted to kinetic energy when the bow is released.