Q. 1. (a) Define 1 Joule and express it in terms of the C.G.S. unit of the physical quantity.
(b) What is the principle of Moments ?
(c) Give 2 ways by which you can change the sense of rotation.
(d) Identify the type of equilibrium :
(i) A raindrop reaching the earth surface with a constant velocity.
(ii) In a beam balance when the beam is in horizontal position.
(e) A, B and C are three forces each of magnitude 4N :
(i) Which force has the least moment about point 'O' ?
ii) Name the force producing clockwise moment ? Q.2.
(a) A force causes displacement in a body. Can work done be zero in this case ? Give the reason for your answer.
(b) A man exerts a force of 250 N in pulling a cart at a constant speed of 16 ms-1 . Calculate the power spent by the man. [2]
(c) State whether work is done or not :
(i) A man pushes a truck
(ii) A boy climbs up 20 steps on a stair
(d) In what way does the temperature of water at the bottom of a water fall differ from the temperature at the top ? Explain.
(e) Give one characteristic of light that changes and one which do not change during refraction of light.
Q.3. (a) Name the material of prism required for obtaining the spectrum of
(i) Ultraviolet light
(ii) Infrared radiation
(b) State the energy change in the following cases while in use :
(i) An electric iron
(ii) A ceiling fan
(c) With reference to the terms mechanical advantage, velocity ratio and efficiency of a machine, name and define the term that will not change for a machine of a given design.
(d) A body of mass 50 kg has a momentum 3000 kg ms -1 calculate its kinetic energy.
(e) An electromagnetic wave has wavelength 50 Å.
(i) Name the wave
(ii) State its peed in vacuum.
please tell answers of all the question correctly and if you dont know plz dont answer
Answers
Here are your answers
(a)The joule jowl, jool;[1][2][3] symbol: J) is a derived unit of energy in the International System of Units.[4] It is equal to the energy transferred to (or work done on) an object when a force of one newton acts on that object in the direction of the force's motion through a distance of one metre (1 newton-metre or N⋅m). It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889).[5][6][7]
(b)The Principle of Moments states that when a body is balanced, the total clockwise moment about a point equals the total anticlockwise moment about the same point.
(c)The direction of rotation can be changed by changing the point of application of force. The given figure shows the anticlockwise and clockwise moments produced in a disc pivoted at its centre by changing the point of application of force F from A to B.
(d)I don't know both the answers
(e)I also don't know this answer
Sorry for that
2.(a)Work done by the force of gravity on the object is zero. Force of gravity acts in the vertical downward direction and the distance covered the the tiobj of force, the horizontal direction. As there is no displacement in th hence the work done is zero.
(b)Force=200N, velocity=16ms
−1
Power=force×velocity=200N×16ms
−1
=3200W
(c)
(I) Yes work is done
(ii) Yes work is done
(d)Temperature at the bottom is more, because the potential energy at top converts to heat energy when water reaches at bottom, as a result temperature of water at the bottom increases.
(e)In refraction of light, there always takes place bending of light. ... Also frequency, wavelength and speed of light are related to one another by the condition, Speed= frequency times wavelength. Since there is a change in wavelength and frequency does not change so speed also changes.
3.(a)(I)Quartz prism is required for obtaining a spectrum of Ultraviolet light.
(ii)Rock salt prism is used instead of glass prism to obtain infrared spectrum because infrared radiations are absorbed by glass but not by rock salt.
(b)According to this an electric current passing through a resistor will convert the electrical energy into heat energy. Therefore it can be said that in an electric iron the electric energy changes into heat energy.
(c)In ceiling fan, the electrical energy changes into mechanical energy of rotation.
(d) This one I don't know the answer
(e)(i) X-Ray has wavelength 50
A
∘
.
(ii) The speed of the wave in vacuum is 3×10
8
m/s.
(iii) X-Rays are used for detection of fracture in bones.
Hope it helps
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