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Steady rain, giving 5 mm an hour, turns suddenly into a downpour 20 mm an hour and the speed of rain drops falling vertically on to a flat roof simultaneously doubles. The pressure exerted by the falling rain on the roof rises by a factor of

A2
B2√2
C4
D8

Read the given statements and select the correct option.
Statement 1 : The acceleration due to gravity on the moon is only one sixth that on the earth. If the earth and moon are assumed to have same density, then the ratio of the radii of moon and earth will be 1:√6.
Statement 2 : Acceleration due to gravity does not depend upon the density of material.

ABoth statements 1 and 2 are true and statement 2 is the correct explanation of statement 1.
BBoth statements 1 and 2 are true but statement 2 is not the correct explanation of statement 1.
CStatement 1 is true but statement 2 is false.
DBoth statements 1 and 2 are false.

A man moves on his motorbike with constant speed of63 km h^-1. After some time, he takes a U turn and continues to move with the same speed. Time elapsed in taking U turn is 10 s. The magnitude of average acceleration during U turn is

Azero
B1.75 m s^-2
C3.50 m s^-2
D6.30 m s^-2

In an experiment to determine the speed of sound, a gun was fired and an observer at a certain distance (x) away measured the time interval (t) between seeing the flash and hearing the shot. Then the speed of sound in air is calculated by x/t.
Which of the following will affect the result?
(i) Temperature of the environment.
(ii) Pitch of the gunshot.
(iii) Wind blowing from the gunner to the observer.
(iv) Loudness of the gunshot.
(v) Wind blowing from the observer to the gunner.
(vi) Quality of sound by gunshot.

A(i), (iii) and (iv)
B(i), (iii) and (v)
C(i), (ii), (iii) and (vi)
D(ii), (iv), (v) and (vi)

An object of mass m is released from rest from point X which is at a height h above Y and slides down a frictionless slope. The object passes point Y with a velocity u as shown in the given diagram.

A second object of mass 0.5m is released from rest from point Z which is at a height 2h above Y. The velocity with which the second object passes point Y in terms of u is

A2u
B√2u
Cu
D0.5u

DIRECTION : Two tuning forks A and B vibrate with frequencies in the ratio 3 : 8 and their wavelengths in the ratio 4 : 5.

The tuning fork A produces relatively _____.

(A) Shriller sound than tuning fork B.

(B) Flatter sound than tuning fork B.

(C) Louder sound than tuning fork B.

Cocoons of silkworms are used for obtaining silk fibres. The ……A………… of silk worms is known as………B…………while the process of taking out threads from the ……C………… is called …………D………....

AA - shearing , B - pisciculture , C - larva , D – reeling
BA - rearing , B - sericulture , C - larva , D – reeling
CA - tearing , B - pisciculture , C - cocoon , D – reeling
DA - rearing , B - sericulture , C - cocoon , D – reeling

Which one of the following is NOT an example of a separation technique?

Asurgical mask
Bfishing net
Cwater tumbler
Dtea strainer

Sunidhi could see a pointed beam of light on settingup an experiment as shown here. She used sheets P, Q and R made of three different materials respectively. She noticed that when she replaced the sheet P with a sheet made of the same material as sheet Q, then she could see the whole candle.

Which of the following options is correct regarding P, Q and R?

ASheet Q is made of a transparent material.
BSheet R is made of a transparent material.
CSheet P is made of an opaque material.
DAll of these.

Alveoli present in lungs

A increase the surface tension
B are few hundred in number
C have limited blood supply
D increase the surface area.