English Medium Class 9 - CBSE Question Bank Solutions

A car of weight 20000 N climbs up a hill at a steady speed of 8 m/s, gaining a height of 120 m is 100 s. Calculate : work done by the car.

A car of weight 20000 N climbs up a hill at a steady speed of 8 m/s, gaining a height of 120 m is 100 s. Calculate : power of engine of car.

Define power. Give the SI unit of power.

A boy weighing 40 kg carries a box weighing 20 kg to the top of a building 15 m high in 25 seconds. Calculate the power. (g = 10 m/s²)

In an experiment to measure his power, a student records the time taken by him in running up a flight of steps on a staircase. Use the following data to calculate the power of the student :

Number of steps = 28
Height of each step = 20 cm
Time taken = 5.4 s
Mass of student = 55 kg
Acceleration = 9.8 m s⁻²
due to gravity

In loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.
How much work does he do in lifting one box?

In loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.
How much energy is transferred when one box is lifted?

In loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.
If the man lifts 4 boxes per minute, at what power is he working?
(g = 10 m s⁻²)

Which one of the following statements about power stations is not true?

An electric motor raises a load of 0.2 kg, at a constant speed, through a vertical distance of 3.0 m in 2 s. If the acceleration of free fall is 10 m/s², the power in W developed by the motor in raising the load is :

What is meant by atomicity ? Explain with two examples.

What is the atomicity of the following ?

1. Oxygen
2. Ozone
3. Neon
4. Sulphur
5. Phosphorus
6. Sodium

Write the formulae of the following compounds. Also name the elements present in them.

1. Water
2. Ammonia
3. Methane
4. Sulphur dioxide
5. Ethanol

In what form does oxygen gas occur in nature ?

In what form do noble gases occur in nature?

What do the following denote ?

1. N
2. 2N
3. N₂
4. 2N₂

What is the difference between the molecule of an element and the molecule of a compound ? Give one
example of each.

One of the forms of a naturally occurring solid compound P is usually used for making the floors of houses. On adding a few drops of dilute hydrochloric acid to P, brisk effervescence are produced. When 50 g of reactant P was heated strongly, than 22 g of a gas Q and 28 g of a solid R were produced as products. Gas Q is the same which produced brisk effervescence on adding dilute HCl to P. Gas Q is said to cause global warming whereas solid R is used for white-washing.

1. What is (i) solid P (ii) gas Q, and (iii) solid R.
2. What is the total mass of Q and R obtained from 50 g of P ?
3. How does the total mass of Q and R formed compare with the mass of P taken ?
4. What conclusion do you get from the comparison of masses of products and reactant ?
5. Which law of chemical combination is illustrated by the example given in this problem ?

Work out the formula for magnesium hydrogencarbonate.

What are (i) ionic compounds, and (ii) molecular compounds ? Give two examples of each type of compounds.