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Updated on October 17, 2017

Try to Solve

What is force? What are its consequences?

Define contact & non-contact force?

Define the following types of forces

(i) Muscular force

(ii) Friction

(iii) Magnetic force

(iv) Gravitational force

(v) Electrostatic force

Define pressure and state its SI unit.

What is a role of air pressure in filling of a syringe with a liquid medicine?

The pillars holding the track of metro trains have a broad base. Why?

Answer the following questions:

(i) How do astronauts talk to one another on the surface of moon and

why? (ii) If you want to hear a train approaching from far away, why is it more

convenient to put the ear to the track? (iii) How are echoes reduced in auditoriums and cinema halls? (iv) Why do we not hear the screams of a bat?

Write True/False against the following statements.

(a) Oxygen in air is an exhaustible natural resource.

(b) Resources which are present in unlimited quantity in nature are called

exhaustible natural resources.

(c) Wildlife is an exhaustible natural resource.

(d) Under high temperature and pressure, dead plants get slowly

converted to coal.

(e) CNG is less polluting fuel than petrol and diesel.

Write the characteristics and some important uses of coal.

One day Reeta went to a jeweller's shop with her mother. Her mother gave an old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?

What happens when:

(a)Dilute sulphuric acid is poured on a copper plate?

(b)Iron nails are placed in copper sulphate solution? Write word

equations of the reactions involved.

(a) Why copper cannot displace zinc from its salt solution?

(b) Why can wires of coal not be drawn?

(c) What happens when a burning matchstick is brought near the mouth of test tube in which a metal has reacted with sulphuric acid?

Give reasons for the following:

(a)Silver is used in coating of mirrors. (b) Aluminium is used to make

electric wires.

(c)Iron is used to construct bridges and houses. (d) Iron sheets are

galvanized before use.

What is RADAR?

Why do we hear the thunder a little later than we see the flash of lightning?

(a) In our body, which part of the ear receives sound waves?

(b) What may happen if the eardrum is absent from our ear?

The sound from a mosquito is produced when it vibrates its wings at an average rate of 100 vibrations per second. What is the time-period of the vibration?

(a) If the amplitude increases 2 times, by how much times will the loudness increase?

(b) What characteristic of a vibrating body determines loudness?

Explain why the flash of lightening is seen first but the sound of thunder is heard a little later.

Which help us to recognize sound?

On which factors loudness of sound depend?

Write the tips given by Petroleum Conservation Research Association (PCRA) which advises people that how to save petrol/diesel while driving.

Answer the following questions: (i) How do astronauts talk to one another on the surface of moon and

why? (ii)If you want to hear a train approaching from far away, why is it

more convenient to put the ear to the track? (iii)How are echoes reduced in auditoriums and cinema halls? (iv)Why do we not hear the screams of a bat?

Discuss briefly the different methods used for preventing corrosion of metals.

Two boys are riding their bicycles on the same concrete road. One has new tyres on his bicycle while the other has tyres that are old and used. Which of them is more likely to skid while moving through a patch of the road which has lubricating oil spilled over it?

Imagine that an object is falling through a long straight glass tube held vertical; air has been removed completely from the tube. The object does not touch the walls of the tube. Will the object experience any force of friction?

Give reasons

a) Phosphorus is stored under water.

b) Handle of screw driver is not made up of metal.

c) Metallic pan has wooden handle.

d) Bells are made up of metals and of wood.

e) Metals are drawn into wires and beaten into sheets.

Answer the following questions

a) Give 3 examples of each

i) Metals II) Non metals.

b) Why does a copper vessel acquire green coating if it is exposed to moisture for a long time. Writethe reaction also.

c) What is rusting of iron?

Write the reaction also.

d) Write 5 uses of metals.

e) Write 5 uses of non metals.

f) Write the reaction for displacement reaction and explain it.

What are the characteristics of a good fuel?

When a candle burns, is it possible to get the wax back a. after the wax melts? b. after the wax burns? (IIINT: Are these physical changes or chemical changes?)

Another solve

Does any part of our body vibrate when we speak? Name thepart. 1

A simple pendulum makes 30 oscillations in 2 seconds. What is the time period and frequency of its oscillation?

Will force of friction come into play when a rain drop rolls down a glass window pane? 1

List three sources of noise pollution in your locality.

A ball of dough is rolled into a flat chapatti. Name the force exerted to change the shape of the dough. 1

Which of the following is true for all metals?

a. They are hard solids. b. They have high melting and boiling points.

c. They have 1-3 valence electrons. d. They are malleable and ductile. 1

Metal A dipped in a salt of metal B displaces B from the solution their salt solution. This shows that

a. A is more reactive than B. b. B is more reactive than A.

c. both A and B are equally reactive d. No such conclusion can be drawn. 1

Shyam was cooking potato curry on a chulha. To his surprise he observed that the copper vessel was getting blackened from outside. It may be due to:

(a)proper combustion of fuel.(b)improper cooking of potato curry.

(c)improper combustion of the fuel.(d) burning of copper vessel 1

Coal is formed from the remains of

(a) vegetation only (c) both vegetation and animals

(b) animals only (d) neither vegetation nor animals 1

Choose the correct statement from the following:

(a) It is difficult to transport natural gas through pipes.

(b) The disadvantage of natural gas is that it cannot be used directly for burning in homes.

(c) Natural gas is stored under high pressure as compressed natural gas.

(d) Natural gas cannot be used for power generation. 1

During dry weather, clothes made of synthetic fibre often stick to the skin. Which type of force is responsible for this phenomenon? 2

Two boys are riding their bicycles on the same concrete road. One has new tyres on his bicycle while the other has tyres that are old and used. Which of them is more likely to skid while moving through a patch of the road which has lubricating oil spilled over it? 2

The handle of a cricket bat or a badminton racquet is usually rough. Explain the reason.

Explain why the surface of mortar and pestle (silbatta) used for grinding is etched again after prolonged use? 2

Write two important uses of coke. 2

People usually keep Angethi/burning coal in their closed rooms during winter season. Why is it advised to keep the door open? 2

What do you mean by reactivity series of metals? 2

Manu was heating oil to fry potato chips. The cooking oil all of a sudden caught fire; he poured water to extinguish the fire. Do you think this action was suitable? If yes, why? If not, why not? In such a condition what should Manu have done? 2

We have a stringed musical instrument. The string is plucked in the middle first with a force of greater magnitude and then with a force of smaller magnitude. In which case would the instrument produce a louder sound? 3

Figure shows a man with a parachute. Name the force which is responsible for his downward motion. Will he come down with the same speed without the parachute? Explain.

Answer-Force of gravity. No, without the parachute his speed wills be higher. 3

While playing tug of war (Figure), Preeti felt that the rope was slipping through her hands. Suggest a way out for her to prevent this. Explain.

3

A man is pushing a cart down a slope. Suddenly the cart starts moving faster and he wants to slow it down. What should he do?

Above figure shows a car sticking to an electromagnet. Name the forces acting on the car? Which one of them is larger? 3

Match the items given in Column I with the items of Column II.

Column I Column II

(a) Used for road surfacing (i) Black gold

(b) Natural gas (ii) Vaseline and candles

(c) Petroleum (iii) Bitumen

(d) Paraffin wax (iv) CNG 3

Match the substances in Column A with their applications given in Column B.

Column A Column B

(Substance) (Application)

(a) oxygen (i) for making crackers

(b) copper (ii) for disinfecting water

(c) sulphur (iii) all living beings inhale during breathing

(d) iron (iv) for making electric wires

(e) chlorine (v) for making rails 3

The calorific values of petrol and CNG are 45000 kJ/kg and 50,000kJ/kg, respectively. If you have vehicle which can run on petrol as well as CNG, which fuel will you prefer and why? 3

Manu was heating oil to fry potato chips. The cooking oil all of a sudden caught fire; he poured water to extinguish the fire. Do you think this action was suitable? If yes, why? If not, why not? In such a condition what should Manu have done?

UNSCRAMBLE THESE LETTERS BY USING CLUES AND WRITE CORRECT WORD. 5 x 1 =5

1.A very ancient stringed instrument -AHPR

2.Reflected sound wave-HOEC

3. A very harsh sound-NSEOI

4.Animal of very high sound frequencies audibility-TSAB

5.Sound of a very high frequency-ACIOLNRUTS 5

ANALOGY TYPE QUESTIONS 5x1=5

  1. Zinc : More reactive : : ..................................................... : Less reactive.
  2. Zinc sulphate : Colourless : : Copper sulphate : .................................................. .
  3. .............................................. : Do not react with acids : : ....................................... :

React with acids.

  1. Lightest element: ..................................................... :: Lightest metal: Lithium.

Gold: Yellow : : Copper : ................................................... . 5

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