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Q1. One watt is equal to:
One watt is defined as the power when 1 joule of work is done in 1 second. So 1 W = 1 J/s.
Q2. 250 units of energy means:
In electricity billing, 1 unit = 1 kilowatt hour (kWh). So 250 units means 250 kWh of electrical energy consumed.
Q3. Food grains drying in the sun involves:
Food grains dry in the sun because heat energy from the sun evaporates the moisture in the grains. This is a process involving heat energy transfer.
Q4. Holding a load without moving it does:
Holding a load without moving it involves force but no displacement. Since work = Force × Displacement, and displacement is zero, no work is done.
Q5. A windmill lifting water does:
A windmill uses wind energy to do mechanical work by lifting water. The wind’s kinetic energy is converted into mechanical energy to do work against gravity.
Q6. Decrease in potential energy of a falling object:
When an object falls, its potential energy decreases and is converted into kinetic energy. This follows the law of conservation of energy.
Q7. Energy possessed due to position or shape is called:
Potential energy is the energy stored in an object due to its position (gravitational potential energy) or shape/configuration (elastic potential energy).
Q8. Gravitational potential energy depends on:
Gravitational potential energy = mgh, so it depends on mass (m) and height (h). It does not depend on speed or time.
Q9. If gravitational force acts horizontally, the work done is:
Gravitational force acts vertically downward. If displacement is horizontal (perpendicular to the force), work done = F × s × cos90° = 0.
Q10. One joule is equal to:
One joule is the work done when a force of 1 Newton moves an object through a distance of 1 metre. 1 J = 1 N × 1 m.
Q11. When a falling object reaches the ground, its kinetic energy:
When a falling object hits the ground, its kinetic energy is converted into other forms like heat and sound energy. This is in accordance with the law of conservation of energy.
Q12. Potential energy of a raised object depends on:
Gravitational potential energy = mgh, so it depends on the height of the object above the reference level.
Q13. Household electrical energy consumption is measured in:
Household electricity consumption is measured in ‘units’ (kilowatt hours) by electricity meters. 1 unit = 1 kWh.
Q14. The total energy before and after transformation remains:
According to the law of conservation of energy, the total energy before and after transformation remains constant. Energy can neither be created nor destroyed.
Q15. A donkey carrying a load on its back does:
If the donkey walks horizontally while carrying a load, the force (weight of load) is vertical while displacement is horizontal. Since they are perpendicular, work done is zero.
Q16. Work done is defined as:
Work done is defined as the product of force and displacement in the direction of force. W = F × s.
Q17. Stopping a moving object requires:
To stop a moving object, force must act opposite to the direction of motion. Work done by this stopping force is negative because force and displacement are opposite.
Q18. According to the law of conservation of 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.
Q19. An electric heater rated 1500 W uses energy in:
Electrical energy consumption is measured in units (kWh) for billing purposes. 1 unit = 1 kWh.
Q20. Energy possessed due to motion is called:
Kinetic energy is the energy possessed by an object due to its motion. KE = ½mv².
Q21. The unit of work is:
The SI unit of work is the joule (J). 1 J = 1 N × 1 m.
Q22. Four devices of 500 W each have total power:
Total power = 4 × 500 W = 2000 W = 2 kW.
Q23. 2000 W is equal to:
1 kW = 1000 W. So 2000 W = 2000/1000 = 2 kW.
Q24. When an engine pulls a train, the work done is:
When an engine pulls a train, force is applied in the direction of motion. So the work done is positive (force and displacement in same direction).
Q25. A satellite moving in a circular orbit experiences work by gravity as:
In circular motion, the gravitational force is perpendicular to the direction of motion (towards centre, while displacement is tangential). Work = F × s × cos90° = 0.
Q26. The formula for gravitational potential energy is:
Gravitational potential energy = mgh, where m is mass, g is acceleration due to gravity, and h is height.
Q27. The energy used in one hour at the rate of 1 kW is called:
Energy = Power × Time = 1 kW × 1 hour = 1 kilowatt hour (kWh). This is also called 1 unit of electricity.
Q28. Work done is zero when:
Work = Force × Displacement. If displacement is zero, work done is zero regardless of the force applied.
Q29. While riding a bicycle, energy changes from:
While riding a bicycle, the chemical energy stored in the rider’s body (from food) is converted into mechanical energy to move the bicycle.
Q30. One joule is equal to:
One joule is the work done when a force of 1 Newton moves an object through a distance of 1 metre in the direction of force.
Q31. 1 kW h is equal to:
1 kWh = 1000 W × 3600 s = 3,600,000 J = 3.6 × 10⁶ J.
Q32. 60 W is equal to:
1 kW = 1000 W, so 60 W = 60/1000 = 0.06 kW.
Q33. When a rock does not move despite pushing, energy is:
When you push a rock and it doesn’t move, the energy you expend is converted into heat due to friction between your hands and the rock. Energy is not destroyed.
Q34. An object capable of doing work possesses:
Energy is defined as the capacity to do work. If an object can do work, it possesses energy.
Q35. The energy consumed by the bulb in one day is:
For a 60 W bulb used for 6 hours: Energy = 60 W × 6 h = 360 Wh = 0.36 kWh. (Based on typical question context)
Q36. Acceleration can be zero when:
When balanced forces act on an object, the net force is zero, so acceleration is zero. The object either remains at rest or moves with constant velocity.
Q37. Energy consumed is calculated using:
Energy consumed = Power × Time. For electrical energy, E = P × t, where P is power in watts and t is time in hours.
Q38. 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).
Q39. Swimming in a pond involves work because:
When swimming, the swimmer applies force against water and moves through it. Since force causes displacement, work is done.
Q40. Energy exists in nature in:
Energy exists in many forms including mechanical, thermal, chemical, electrical, nuclear, light, sound, etc.
Q41. The SI unit of power is:
The SI unit of power is the watt (W), named after James Watt. 1 W = 1 J/s.
Q42. Power is defined as:
Power is the rate of doing work or rate of energy transfer. Power = Energy / Time = Work / Time.
Q43. The law of conservation of energy is valid for:
The law of conservation of energy is a universal law. It is valid in all situations, from microscopic to macroscopic systems.
Q44. The bulb consumes how many units per day?
For a 60 W bulb used for 6 hours: Energy = 60 × 6 = 360 Wh = 0.36 kWh = 0.36 units.
Q45. Work done by gravity on an object thrown up and coming back to the same level is:
When an object is thrown up and returns to the same level, the displacement is zero (initial and final positions same). Work done by gravity = mg × displacement = 0.
Q46. The unit of energy is the same as the unit of:
Energy and work have the same SI unit: the joule (J). Energy is the capacity to do work, so they are measured in the same unit.
Q47. Lighting of a bulb by a battery involves conversion of:
A battery stores chemical energy. This is converted to electrical energy, which then produces light and heat in the bulb.
Q48. One ‘unit’ of electrical energy is equal to:
One ‘unit’ of electrical energy is 1 kilowatt hour (kWh), which is the standard billing unit for electricity.
Q49. The power rating of the electric bulb given is:
A typical household electric bulb has a power rating of 60 W. This means it consumes 60 joules of energy per second.
Q50. The formula for kinetic energy is:
Kinetic energy is given by KE = ½mv², where m is mass and v is velocity. Kinetic energy depends on mass and the square of velocity.