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X1=mu/k, x2=2mu/k, x3=3mu/k.

Power of lens is reciprocal of focal length of lense in meter P=1/f f in meter f=1/2=0.5 meter=50 cm Since focal length is positive, lense is convex

Distance travelled by airoplane is given by a formula S=ut+1/2at2 Where u is initial velocity=0 t is time for total travel=12 sec a is acceleration of airoplane=6m/s2 S=ut+1/2at2 =0×12+1/2×6×12×12 =432 mtr

Step1: Whenever you have this kind of question the simple thing you can to do is to observe how many digits are there after decimal. ( *Here in question We have three digits after decimal)

Step2 : Now you have to multiply and divide with one proceeding with Three zeros that is 1000 so we get (1*1000)/(1000 * 0.002)               

We get 1000/2=500         

Therefore the Answer is 500

Hope this will help you, Happy learning

I totally agree with the previous answer. I would also like to add,

The Moon's gravity is not strong enough to pull the entire land mass of the Earth, but it is strong enough to pull just water towards itself. 

You can understand it, when you understand water is fluid. The particles in fluid are not tightly bound. They get easily pulled. Whereas, the land mass is solid and the particles in a solid are tightly bound. So, when Moon tries to pull solid, it is actually trying to pull the entire Earth(as a whole solid) and the Moon's gravitational pull is not strong enough to pull the solid Earth. 

So, now you can see, why only the water is pulled by the Moon's gravity. And how tide's are formed.

Frequency is inversely proportional to Time period.

Freq = 1/Timeperiod

Given,

Time period = 0.002 seconds

Therefore,

Frequency = 1/ 0.002 = 1000 / 2 = 500 Hertz

Final answer,

Frequency = 500 Hz

Measurement is the comparision of unknown quantity (length, temperature etc) to a known standard (Rular Scale, Thermometer etc)

The electric charge is conserved. Mass of body is not conserved.

The density and the refractive index of the atmosphere decreases with altitude, so the rays above and below the sun on the horizon are retracted by different degrees. This causes the apparent flattering of the sun.

A gun moves backward when a shot is fired because according to third law of motion "Every action has an opposite and an equal reaction"so when shot is fired we are acting and in return we will get reaction.

Also, The gun will have recoil velocity with negative sign which indicates that the gun moved in opposite direction of shot.