HARD
9th CBSE
IMPORTANT
Earn 100

Two students X and Y have to do their experiment on plotting the temperature-time graph for a hot body as it cools to room temperature. They do their experiments in the same lab, using completely identical apparatus, take equal amounts of tap water heated up to the same temperature, start their observations simultaneously and note the temperature values at identically spaced intervals of time. Their temperature-time graphs, plotted on a given graph paper, with the same given choices of scales along the axis, are however, as shown: The following could be the reason for this difference:

(A) Use of an overhead fan by student X.
(B) Use of an overhead fan by student Y.
(C) Less frequent stirring of water by student X.
(D) Less frequent stirring of water by student Y.
The most likely reason is:

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Important Questions on Sound

EASY
9th CBSE
IMPORTANT
Science for Ninth Class Part 1 Physics>Chapter 5 - Sound>Exercise 3>Q 11
In the set up shown the weight of the body was measured in air and in water. The reading of mark X in the spring balance would be :

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EASY
9th CBSE
IMPORTANT
Science for Ninth Class Part 1 Physics>Chapter 5 - Sound>Exercise 3>Q 12
While performing an experiment on verifying the laws of reflection of sound, the 'reflected sound' can be detected better by keeping one ear :
EASY
9th CBSE
IMPORTANT
Science for Ninth Class Part 1 Physics>Chapter 5 - Sound>Exercise 3>Q 13
A student uses a spring balance of the least count 10 g wt and range 500 g wt. He records the weight of small iron cube in air, in tap water and in a concentrated solution of common salt in water. If his three readings taken in this order are W1, W2, W3. He is likely to observe that:
EASY
9th CBSE
IMPORTANT
Science for Ninth Class Part 1 Physics>Chapter 5 - Sound>Exercise 3>Q 14
In an experiment to determine the densities, four solids A, B, C and D are immersed in a liquid contained in a measuring cylinder, one by one. The volumes of water displaced by the solids A, B, C and D are 100 cm3,100 cm3, 80 cm3 and 80 cm3, respectively. When weighed in air, the masses of solids A, B, C and D were found to be 80 g, 100 g, 100 g and 80 g, respectively. The two solids having identical densities are:
MEDIUM
9th CBSE
IMPORTANT
Science for Ninth Class Part 1 Physics>Chapter 5 - Sound>Exercise 3>Q 15
A student is given an iron cube of side 1 cm, a measuring cylinder of range 100 mL and least count 1 mL, and a spring balance of range 100 g wt and least count 1 g wt. He can use these to measure :
HARD
9th CBSE
IMPORTANT
Science for Ninth Class Part 1 Physics>Chapter 5 - Sound>Exercise 3>Q 16
Four beakers are labelled as P,Q, R and S. A student puts salt solutions of different concentrations in the four beakers without spring balance gives a reading of 150g in air. When this solid, while still suspended from the hook of spring balance, is fully immersed in beakers P,Q, R and S, the readings shown by the spring balance in the four beakers P,Q, R and S are 110g,130g,140g and 120g respectively. The most concentrated solution is contained in the beaker labelled as:
EASY
9th CBSE
IMPORTANT
Science for Ninth Class Part 1 Physics>Chapter 5 - Sound>Exercise 3>Q 17
While doing an experiment on plotting the temperature-time graph of hot water as it cools, we can get a good graph:
HARD
9th CBSE
IMPORTANT
Science for Ninth Class Part 1 Physics>Chapter 5 - Sound>Exercise 3>Q 18

A student heats some amount of tap water in a calorimeter to a temperature of nearly 50°C above the room temperature. He then records the temperature of this water as it is cooling down at regular intervals of 2 minutes each. He tabulates his observations as follows:

Time (in minutes) → 0 2 4 6 8 10
Temperature (in ºC) → t1 t2 t3 t4 t5 t6
He is likely to observe that: