Physics Q Phobia

Obtain equations of motion for constant acceleration, using method of calculus.

2019-02-02T00:43:00.002+05:30

A car is moving along a straight line, say OP in fig 3.11. It moves from O to P in 18 s and return from P to Q in 6.0 s. What are the average velocity and average speed of the car in going (a) from O to P and (b) from O to P and back to Q ?

2019-02-02T00:42:00.002+05:30

“The distances traversed, during equal intervals o time, by a body falling from rest, stand to one another in the same rate as the odd numbers beginning with unity [namely, 1:3:5:7…..]”. Prove it.

2019-02-01T00:48:00.001+05:30

The position of an object moving along x-axis is given by x = a+ bt2 where a = 8.5 m, b = 2.5 m s-2 and t is measured in seconds. What is its velocity as t = 0 s and t = 0.2 s. What is the average velocity between t = 2.0 s and t = 4.0 s?

2019-02-01T00:47:00.001+05:30

A famous relation in physics relates ‘moving mass’ m to the ‘rest mass’ m0 of a particle in term of its speed v and the speed of light, c [ This relation first arose as a consequence of special relativity due to Albert Einstein]. A boy recalls the relation almost correctly but forgets where to put the constant c. He writes: m= m_0/〖(1- v^2)〗^(1/2)

2019-01-27T01:57:00.002+05:30

A book with many error contains four different formulas for the displacement y of a parties undergoing a certain periodic motion : (a) y = a sin 2π t/T (b) y = a sin vt (c) y = (a/T) sin t/a (d) y = (a √2 (sin 2π t/T + cos 2π t/T) (a = maximum displacement of the particle, v = speed of the particle, T = time-period of motion), Rule out the wrong formulas on dimensional grounds.

2019-01-27T01:54:00.002+05:30

A physical quantity P is related to four observables a, b, c and das follows: P = a3b 2 / √(c ) d The percentage error of measurement in a, b, c and d are 1% 3% 4% and 2%, respectively. What is the percentage error in the quantity p? If the value of p calculated using the above relation turns out to be 3.763, to what value should you around off the result?

2019-01-27T01:29:00.002+05:30

The mass of a box measured by a grocer’s balance is 2.300 kg. Two gold pieces of masses 20.15 g and 20.17 g are added to a box. What is (a) the total mass of a mass of the box, (b) the difference in the masses of the pieces to correct significant figures?

2019-01-27T01:20:00.000+05:30

The length, breadth and thickness of a rectangular sheet of metal are 4.234 m, 1.005 m, and 2.01 cm respectively. Give the area and volume of the sheet to correct significant figures.

2019-01-27T00:12:00.002+05:30

State the number of significant figures in the following: 0.007 m^2 (b) 2.64 x 10^24 kg (c) 0.2370 g cm^(-2) (d) 6.320 J (e) 6.032 N m^(-2) (f ) 0.0006032 m^2

2019-01-25T16:04:00.002+05:30

The photograph of a house occupies an area of 1.75 cm2 on a 35 mm slide. The slide is projected on to a screen, and the area of the house on the screen is 1.55 m2. What is the linear magnification of the projector-screen arrangement?

2019-01-25T16:02:00.000+05:30

Answer the following: (a) You are given a thread and a metre scale. How will you estimate the diameter of the thread? (b) A screw gauge has a pitch of 1.0 mm and 200 divisions on the circular scale. Do you think it is possible to increase the accuracy of the screw gauge arbitrarily by increasing the number of divisions on the circular scale? (c) The mean diameter of a thin brass rod is to be 2 measured by vernier callipers. Why is a set of 100 measurements of the diameter expected to yield a more reliable estimate than a set of 5 measurements only?

2019-01-25T15:59:00.002+05:30

A Student measure the thickness of a human hair by looking at it through a microscope of magnification 100.He measure 20 observations and finds that the average width of the hair in the field of view of the microscope is 3.5 mm. What is the estimate on the thickness of air?

2019-01-25T15:55:00.002+05:30

Which of the following is the most precise device for measuring length? (a) A vernier callipers with 20 divisions on the sliding scale (b) A screw gauge of pitch 1 mm and 100 division’s sliding scale on the circular scale (c) An optical instrument that can measure length to within a wavelength of light

2019-01-25T15:52:00.001+05:30

A new unit of length is chosen such that the speed of light in vacuum is unity. What is the distance between the sun and the Earth in term of the new unit if light takes 8 min and 20 s to cover this distance?

2019-01-24T23:59:00.002+05:30

Explain this statement clearly: “To call a dimensional quantity ‘large’ or ‘small’ is meaningless without specifying a standard for meaning.” In view of this, reframe the following statement wherever necessary: a) Atoms are very small objects b) A het plane moves with great speed c) The mass of Jupiter is very large d) The air inside this room contain a large number of molecules e) A protons is much more massive than an electron f) The speed of sound is much smaller than the speed of light.

2019-01-24T23:56:00.002+05:30

A calorie is a unit of heat or energy and it equals about 4.2 J where 1 J = 1 kg m2 s-2 Suppose we employee a system of units in which the unit of mass equal α kg, the unit of length equal β m, the unit of time is γ s. Show that a calorie has a magnitude 4.2 α -1 β -2 γ 2 in term of the new units.

2019-01-24T23:49:00.002+05:30

Fill in the blanks (a) 1 kg m3 = …… g cm2 a-2 (b) 1 m = …….. ly (c) 3.0 m s-2 = …….. km h-2 (d) G = 6.67 x 10-11 N m2 (kg)-2 = …… (cm)3 s-2 g-1.

2019-01-24T23:42:00.000+05:30

Fill in the blanks (a) The volume of a cube of side 1 cm is equal to …….. m3. (b)The surface area of a solid cylinder of radius 2.0 cm and height 10.0 cm is equal to ….. (mm)2 (c) A vehicle moving with a speed of 18 km h-1 cover …… m in 1 s. (d) The relative density of lead is 11.3. Its density is …. G cm-3 or ….. Kg m-3.

2019-01-24T23:37:00.000+05:30

Consider a simple pendulum, having a bob attached to a string that oscillates under the action of the force of gravity. Suppose that period of oscillation of the simple pendulum depends on its length (l), mass of the bob (m) and acceleration due to gravity (g). Derive the expression for its time period using method of dimensions.

2019-01-24T02:03:00.003+05:30

The SI unit of energy is J = kg m2 s-2; that of speed v is m s-1 and of acceleration a is m s -2. Which of then formulae for kinetic energy (k) given below can you rule out on the basis of dimensional arguments (m stand for the mass of the body)? (a) K = m2v3 (b) K = (1/2) mv2 (c) K = ma (d) K = (3/16) mv2 (e) K = (1/2) mv2 + ma

2019-01-24T01:58:00.000+05:30

Let us consider an equation 1/2 m v2=mgh Where m is the mass of the body, v its velocity g is the acceleration due to gravity and h is the height. Check whether this equation is dimensionally correct.

2019-01-24T01:48:00.002+05:30

5.74 g of a substance occupied 1.12 cm3. Express its density by keeping the significant figure in view.

2019-01-24T01:43:00.002+05:30

Each side of a cube is measured to be 7.203m. What are the total surface area and the volume of the cube to appropriate significant figures?

2019-01-24T01:39:00.000+05:30

The period of oscillation of a simple pendulum is T = 2π √L/g. Measured value of L is 20.0 cm known to 1mm accuracy and time for 100 oscillation of the pendulum is found to be 90 s using a wrist of 1 s resolution. What is the accuracy in the determination of g?

2019-01-22T00:58:00.003+05:30