(i) (a) In the following atoms, which one isa radioisotope? Give one use of this isotope. O¹⁶,C¹⁴, N¹⁴, He⁴

(b) Name the class of the lever shown in the picture below:



(ii) Fill in the blanks:

(a) When a stone tied to a string is rotated in a horizontal plane, the tension in the string provides _______ force necessary for circular motion.
(b) Work done by this force al any instant is _____

(iii) A non uniform beam of weight 120 N pivoted at one end is shown in the diagram below. Calculate the value of F to keep the beam in equilibrium.


(iv) Meera chose to use a block and tackle system of '9' pulleys instead of a single movable pulley to lift a heavy load.

(a) What is the advantage of using a block and tackle system over a single movable pulley?
(b) Why should she connect more number of pulleys in the upper fixed block?

(v) Sumit does 600 J of work in 10 min and Amit docs 300 J of work in 20 min. Calculate the ratio of the powers delivered by them.

(vi) 5 bulbs are connected in series in a room. One bulb is fused. It is removed and remaining 4 bulbs are again connected in series to the same circuit, What will be the effect on the following physical quantities? (Increases, Decreases, Reinain Same)

(a) Resistance
(b) Intensity of light

(vii) Rohan conducted experiments on echo in different media. He observed that a minimum distance of ‘x' meters is required for the echo to be heard in oxygen and ‘y’ meters in benzene. Compare ‘x’ and ‘y’ Justify your answer.

Speed of sound in oxygen: 340 ms^-1
Speed of sound in benzene: 200 ms^-1

Solution

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