High School

1. If a car is moving with the speed of 36 km/hr, convert it into m/s.

2. If a car travels a distance of 900 m in 30 seconds, what will be the speed of the car?

3. The velocity of a taxi increases from 5 m/s to 20 m/s in 15 seconds, what will be the acceleration of the taxi?

4. A bus is moving with a speed of 10 m/s. How much distance does it cover in 20 seconds?

5. A man throws a stone of mass 3 kg and the stone falls down 500 meters from him. What is the work done by him?

6. If a worker moves a mass of 60 kg through 300 metres in 1 minute, what is his power?

7. A man of weight 450 N carries a weight of 150 N and climbs up through a height of 3 meters in 10 seconds. What is his power?

Answer :

Let's solve each part of the question step-by-step.

  1. Convert 36 km/hr to m/s:

    To convert from kilometers per hour (km/hr) to meters per second (m/s), use the conversion factor: 1 km/hr = [tex]\frac{1}{3.6}[/tex] m/s.

    [tex]36 \text{ km/hr} = 36 \times \frac{1}{3.6} \text{ m/s} = 10 \text{ m/s}[/tex]

  2. Calculate the speed of a car traveling 900 m in 30 seconds:

    Speed is calculated by dividing distance by time.

    [tex]\text{Speed} = \frac{\text{Distance}}{\text{Time}} = \frac{900 \text{ m}}{30 \text{ s}} = 30 \text{ m/s}[/tex]

  3. Acceleration of the taxi:

    Acceleration is the rate of change of velocity over time. Use the formula:

    [tex]\text{Acceleration} = \frac{\text{Final Velocity} - \text{Initial Velocity}}{\text{Time}}[/tex]

    Given: Initial velocity = 5 m/s, Final velocity = 20 m/s, Time = 15 s.

    [tex]\text{Acceleration} = \frac{20 \text{ m/s} - 5 \text{ m/s}}{15 \text{ s}} = 1 \text{ m/s}^2[/tex]

  4. Distance covered by a bus moving at 10 m/s for 20 seconds:

    The formula for distance is:

    [tex]\text{Distance} = \text{Speed} \times \text{Time}[/tex]

    [tex]\text{Distance} = 10 \text{ m/s} \times 20 \text{ s} = 200 \text{ m}[/tex]

  5. Work done by a man throwing a stone:

    If the stone is thrown horizontally and falls down due to gravity, the work done directly by the man against gravity is zero because his force in throwing is horizontal. However, if we consider potential energy, the formula is:

    [tex]\text{Work Done} (W) = \text{Weight} \times \text{Height} = 3 \text{ kg} \times 9.8 \text{ m/s}^2 \times 500 \text{ m}[/tex]

    [tex]W = 14700 \text{ J (joules)}[/tex]

  6. Power of a worker moving a mass of 60 kg through 300 m in 1 minute:

    Power is the rate at which work is done. First, calculate work done:

    [tex]\text{Work Done} (W) = \text{Force} \times \text{Distance} = 60 \text{ kg} \times 9.8 \text{ m/s}^2 \times 300 \text{ m}[/tex]

    [tex]W = 176400 \text{ J}[/tex]

    Time = 1 minute = 60 seconds.

    [tex]\text{Power} (P) = \frac{\text{Work}}{\text{Time}} = \frac{176400 \text{ J}}{60 \text{ s}} = 2940 \text{ W (watts)}[/tex]

  7. Power of a man carrying weight climbing 3 meters in 10 seconds:

    Total weight = 450 N (weight of man) + 150 N = 600 N.

    Work done (W) = Weight [tex]\times[/tex] height = 600 N [tex]\times[/tex] 3 m = 1800 J.

    [tex]\text{Power} (P) = \frac{\text{Work}}{\text{Time}} = \frac{1800 \text{ J}}{10 \text{ s}} = 180 \text{ W}[/tex]

This approach uses fundamental concepts of physics to solve each part clearly and is accessible to high school students. Always ensure that any calculations involving units are consistent.

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