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Name several repetitive phenomenon occurring in nature which could serve reasonable times standards

  1. Give the drawback to use the period of a pendulum as time standard.
    1. Why do we find it useful to have two units for the amount  of substance  kilogram and the mole?
    2. Three students measured the length of a needle with  a scale on which  minimum  division is 1mm and recorded as (i) 0.2145m  (ii) 0.21m (iii) 0.214m which record  is correct any why?
    3.  An old saying is that “A  chain is only  as strong as its weakest link”. What  analogous statement can you make regarding experimental data  used in a computation?
    4. The period  of simple pendulum is measured by a stop watch what type or errors  are possible in the time period?
    5. Does a dimensional analysis give any information  on constant of proportionality that may appear  in an algebraic expression? Explain.
    6. Write the dimensions of (i) Pressure (ii) Density
    7. The  wavelength HOW TO ATTEMPT MCQs Ilm Ki Roshni  of a wave depends  on the speed v of the wave and its frequency f. Knowing that

[HOW TO ATTEMPT MCQs Ilm Ki Roshni] = [HOW TO ATTEMPT MCQs Ilm Ki Roshni],                  [v] = [HOW TO ATTEMPT MCQs Ilm Ki RoshniT-1]                and [f] = [T]-1

 Decide which of the followings id correct,  f = VHOW TO ATTEMPT MCQs Ilm Ki Roshni  or  f = HOW TO ATTEMPT MCQs Ilm Ki Roshni


  1. A light  year is the distance light travels in one year. How may meters are there one  light year: (speed of light = 3.0 x 108  ms-1).

(Ans: 9.5 x 1015m)

  1. a) How many seconds are there in 1 year?

b) How many  nanoseconds in 1 year?

c) How many  years in 1 second? 

                        [Ans. (a) 3.1536 x 107 s, (b) 3.1536 x 1016 ns (c) 3.1 x 10-8 yr] 

  1. the length and width of a rectangular  plate are measured to be 15.3 cm and 12.80 cm, respectively. Find the area of the plate.                          

(Ans: 196cm2)

  1. Add the following  masses given in kg up to appropriate precision 2.189, 0.089, 11.8 and 5.32.

(Ans: 194.4 Kg)

  1. Find the value of ‘g’ and its uncertainty using  T= 2HOW TO ATTEMPT MCQs Ilm Ki RoshniHOW TO ATTEMPT MCQs Ilm Ki Roshni from the  following  measurements made  during an experiment

Length of simple pendulum HOW TO ATTEMPT MCQs Ilm Ki Roshni = 100 cm

Time  of r20 vibrations = 40.2 s

Length was measured by a metre scale of accuracy up to  1 mm and time by stop watch of accuracy up to 0.1s.

                                                                                    (Ans: 9.76 HOW TO ATTEMPT MCQs Ilm Ki Roshni 0.06 ms-2)

  1. What are the dimensions and units of gravitational constant G in the formula HOW TO ATTEMPT MCQs Ilm Ki Roshni.

(Ans: [HOW TO ATTEMPT MCQs Ilm Ki Roshni], Nm2 Kg-2)

  1. Show that the expression HOW TO ATTEMPT MCQs Ilm Ki Roshniis dimensionally correct, where HOW TO ATTEMPT MCQs Ilm Ki Roshni is the velocity at t=0, a is acceleration and HOW TO ATTEMPT MCQs Ilm Ki Roshniis the velocity at time t.
    1. The speed v of sound waves through a medium may be assumed to depend on (a) the density HOW TO ATTEMPT MCQs Ilm Ki Roshniof the medium and (b) its modules of elasticity E which is the ratio of stress to strain. Deduce by the method of dimensions, the formula for the speed of sound.
  1. Show that the famous “Einstein equation” E= mc2 is dimensionally consistent.
    1. Suppose, we are told that the acceleration of a particle moving in a circle of radius r with uniform speed v is proportional to some power of r, say rn, and some power of v, say vm, determine the powers of r and v?

(Ans: n = -1, m=2)

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