Rustomjee Cambridge International School & Junior College
2nd TERM EXAMINATION (2012-13)SUBJECT: PHYSICS Std: VII Div.___
---Question Number 1 2 3 4 5 6 7 8 9 10 Total
Marks Obtained
Q.1) Choose the correct alternatives. [10]
1) Sound waves travel fastest in:
A) air B) metals C) vacuum D) liquids 2) Sounds with frequency less than 20 Hz are called:
A) supersonic B) ultrasonic C) sonar D) infrasonic 3) In sitar, sound is produced by:
A) beating B) rubbing C) blowing D) plucking
4) The frequency of a vibrating string does not depend on A) the tension in the string B) the length of the string
C) the temperature of the surroundings D) the thickness of the wire 5) Compared to long pipe, a shorter pipe emits a:
A) louder note B) lower note C) higher pitched note D) softer note 6) An example of a percussion instrument is
A) Violin B) harmonium C) tabla D) trumpet
7) The speed of sound in air is
A) 250 m/s B) 340 m/s C) 400 m/s D) 380 m/s
Name:___________________________________________________ Roll No. : _______
8) An instrument used to measure the depth of the sea is
A) sonar B) radar C) barometer D) thermometer 9) The intensity of sound is measured in the units of
A) joule B) watts C) decibel D) none of these 10) ______________________ are the characteristics of sound.
A) frequency & amplitude B) compressions & rarefactions C) crests & troughs D) pitch, loudness & timbre
11) Alcohol is a good thermometric liquid for measuring low temperatures because it A) wets glass B) is a colourless liquid
C) is a good conductor of heat D) has a very low freezing point 12) If two solids are in contact, flow of heat by conduction will take place only if:
A) they are metals B) they are large in size
C) they are at different temperatures D) they are good insulators of heat 13) A liquid is heated .Which statement is incorrect?
A) The molecules expand. B)The molecules gain energy.
C) The molecules move further apart. D) The molecules move faster. 14) Iceboxes are double-walled containers
A) to make it strong B) to make it attractive C)to prevent the outside heat from entering the box D) none of these
15) The principle of bimetallic strip is to convert heat energy into ________
A) mechanical movement B) magnetism C) electricity D) steam
16) When a substance has a fixed mass, volume & shape it is in _______. A) solid B) molten C) combined D) gaseous
17) By process of convection, the transfer of heat is always
A) upwards B) downwards C) sideways D) in all possible directions 18) The top of the mercury thread in a mercury in glass thermometer
reaches point X at 0 °C and point Z at 100 °C. Where might it be at a temperature below the ice-point?
A) point W B) point X C) point Y D) point Z
19) The number of divisions between lower and upper fixed points in the Fahrenheit scale is
A) 100 B) 80 C) 180 D) all of three
20) Four sound waves W, X, Y and Z are displayed by an oscilloscope screen. The oscilloscope settings are the same in each case.
Which two sounds have the same pitch?
A) W and X B) W and Y C) X and Y D) X and Z
Q.2] Answer the following questions:--
Tick the three correct statements. The particles in liquid
are further apart than in a solid
are arranged in a more fixed pattern than in a solid move about randomly
vibrate about a fixed point are further apart than in a gas move all of the time
B) Convert the following:--
i) 1040F into 0C [2] _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ ii) 1200C into K [2]
_______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________
Bats emit short bursts of ultrasound. The echoes of the ultrasound help the bat find insects and prevent the bat flying into objects.
a) State what is meant by an echo. [1]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ b) State
i) the approximate range of frequencies of sound audible to humans, [1]
_________________________________________________________________________ ii) How the frequency of ultrasound differs from frequencies in this audible range. [1]
_________________________________________________________________________ _________________________________________________________________________ c) State two uses of ultrasonic sound. [2]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ ________________________________________________________________________ d) An ultrasonic signal is sent from a ship towards the bottom of the sea. It is received
back after 1.5s. What is the depth of the sea? ( Given speed of sound in sea water is 1530m/s). [3]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ Q.3]1. Observe the diagram and answer the following questions:-
a) Indentify the type of breeze. [1]
_________________________________________________________________________
b) Give reason for your answer in (a) above. [3]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________
2. Observe the following diagram and answer the given questions. [4]
Sea
Land
Vacuum pump is closed air is being removed air is completely removed
a. In which case the sound of clock is heard?
_________________________________________________________________________ b. What happens to the sound of clock in B?
_________________________________________________________________________ c. Will you be able to hear the sound of clock in C? _________________
d. Give appropriate reason for your answer in question c.
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ 3. Riya wants to buy some shirts for daily use. Following pictures shows few options she
has. Which shirt should be bought keeping in mind the season that she is going to wear the shirt. [4]
A B
a. Summer season : ______________________________________________ b. Winter season : ________________________________________________
Give reasons for your answers in questions a and b?
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________
_________________________________________________________________________ _________________________________________________________________________ 4. While walking between certain buildings a
teenager notices that there is a clear echo of her talking. She asks a friend to help her to use this effect to find the speed of sound. She makes a loud noise by hitting a metal
sheet with a metal hammer. She asks her friend to start a stop clock when she hits the metal sheet and stop it when she hears the echo.
(a) (i) Use a ruler to measure the distance, d in centimeters, from the girl to the wall in Fig. =_______________________________________ cm [1]
(ii) Use the scale shown to calculate the actual distance in metres, travelled by the noise from the girl to the timer.
Actual distance travelled by the noise
= ___________________________________________ m [3]
(iii) Table shows the times of five repeats of the experiment.
The time for experiment 5 is much longer than the others, and should be discarded. Suggest a reason that may have caused this longer time. [1]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ (iv)Calculate the average time in seconds, using data from experiments 1, 2, 3 and 4.
average time = ____________________________________________seconds [2]
(v) Calculate the speed of sound, by dividing the distance found in (a)(ii) by the time found in (a)(iv).
speed of sound =
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________
_____________________________________________________________ m / s [2]
(vi) The actual speed of sound in the air is 343 m / s. Comment on the accuracy of your value.
_________________________________________________________________________ _________________________________________________________________________
_______________________________________________________________________[1]
5. (a) A student is investigating how much heat is produced in the reaction between solid A and solution B.
• He places 25 cm3of solution B in a plastic cup.
• He measures the temperature.
• He adds a sample solid A to solution B and starts the stopclock.
• He measures the temperature of the mixture every half minute for seven minutes, Stirring throughout, and records the values in Table
Read the thermometers in Fig , which show the temperatures of the mixture at 0, 2.5 and 4.0 minutes, and record the values in Table [3]
6. A boy is investigating the properties of materials. He puts four rods in a beaker of boiling water. After 3 minutes, he tests the temperature of each rod by touching the top.
a) Which rod will feel hottest? [1]
_________________________________________________________________________ _________________________________________________________________________
b) Good conductors have wide uses. List any 2 uses.
[2]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________
c) Bad conductors are also very useful in our everyday life. List any 2 uses. [2]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________
d) Compare with 2 points each between conductors & insulators. [2]
7. Fig shows the waveform of the note from a bell. A grid is given to help you take measurements.
a) i) State what, if
anything, is happening to the
loudness of the note. [1]
_________________________________________________________________________ _________________________________________________________________________ ii) State how you deduced your answer to a) i) [1]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ iii) Loudness depends upon some factors. [4]
List those factors & explain any 2 of them.
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ 8. A girl tests a piece of metal wire.
She fixes one end and hangs masses on the other end. The diagram below shows her experiment.
a) Describes what happens to the wire
as more masses are hung on the end. [1]
_________________________________________________________________________ _________________________________________________________________________ b) The girl keeps the masses same but heats the middle of the wire with a Bunsen burner. The wire does not melt. She notices that the wire changes.
Explain what happens to the wire and why this happens. [2]
What happens?
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________
Why this does happens?
_________________________________________________________________________ _________________________________________________________________________ c) i) When telephone and electric wires are connected between two poles, they are kept loose in summer. Explain. [1]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ ii) Ajay is struggling to open a tightly fitted metal cap, how would you help him to open it. [2]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ d) If your hand is close to the lamp when it is switched on for a few seconds,
you can feel warmth from the. By what method has the thermal energy reached
your hand? Tick one box. [1]
conduction convection evaporation radiation
Define the answer you tick. [1]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ 9. A substance can exist in 3 different states. Solids, liquids & gases.
a) The fig below shows the different phases. i) the conversion of a substance from liquid to vapour or gasesous state is known as
vaporisation. Vaporisation may take place in two ways,
_________________________________________________________________________ ii) Compare between them related to the parameters given below. [2]
Parameters 1) where it takes place
2) temperature at which it takes place
iii) Explain freezing point. [1]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ b. Logs of wood are burning in a camp-fire on the ground. A person is sitting nearby.
(a) (i) State two types of energy that the burning logs possess. [1]
______________________________________________________
(ii) State the main method of heat transfer by which energy from the
fire reaches the person sitting nearby. [1]
_________________________________________________________________________ 10. Water is a poor conductor of heat. A beaker of water is heated as
shown in Fig. All the water heats up quite quickly.
a. State the process by which heat spreads most rapidly through the
water. [1]
_________________________________________________________________________ 1._____________________________________________________
b. Draw with help of arrows, in fig given above how, heat is transferred in the beaker. [1]
c. Explain the process mentioned in (a). [1]
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ d. State any one application for the same. [2] _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________
