Physical Quantities

Q. When the planet Jupiter is at a distance of 824.7 million kilometers from the Earth, its angular diameter is measured to be 35.72” of arc. Calculate the diameter of Jupiter

Q.

If the force is given by $F=at+b{t}^2$ with $t$ as time. The dimensions of $a$ and $b$ are

1. $\left[ML{T}^{-4}\right],\left[ML{T}^{-4}\right]$

2. $\left[ML{T}^{-3}\right],\left[ML{T}^{-4}\right]$

3. $\left[M{L}^2{T}^{-3}\right],\left[M{L}^2{T}^{-2}\right]$

4. $\left[M{L}^2{T}^{-3}\right],\left[M{L}^3{T}^{-4}\right]$

Q. The Sun is a hot plasma (ionized matter) with its inner core at a temperature exceeding 10⁷ K, and its outer surface at a temperature of about 6000 K. At these high temperatures, no substance remains in a solid or liquid phase. In what range do you expect the mass density of the Sun to be, in the range of densities of solids and liquids or gases ? Check if your guess is correct from the following data : mass of the Sun = 2.0 ×10³⁰ kg, radius of the Sun = 7.0 × 10⁸m.

Q. A SONAR (sound navigation and ranging) uses ultrasonic waves to detect and locate objects under water. In a submarine equipped with a SONAR, the time delay between generation of a probe wave and the reception of its echo after reflection from an enemy submarine is found to be 77.0 s. What is the distance of the enemy submarine? (Speed of sound in water = 1450 m s¯¹).

Q. 17. if the earth were suddenly contract to 1/nth of its present radius without any change in its mass, the duration of new day will be

Q. One mole of an ideal gas at standard temperature and pressure occupies 22.4 L (molar volume). What is the ratio of molar volume to the atomic volume of a mole of hydrogen ? (Take the size of hydrogen molecule to be about 1 Å). Why is this ratio so large ?

Q. 24. According to Keplers third law T square is proportional to R cube here the proportionality constant is K. If mass of sun and a planet is M and m respectively. Then the relation between gravitational constant G and K is

Q. 44 Find time taken by particle in going from x=A/2 to x=A

Q.

A tube closed at one end and containing air is excited. It produces the fundamental note of frequency 512 Hz. If the same tube is open at both the ends the fundamental frequency that can be produced is

[RPET 1999]

1. 1024 Hz

2. 512 Hz

3. 256 Hz

4. 128 Hz

Q. A: All physically correct equations are dimensionally correct.R: All dimensionally correct equations are physically correct

Q. 13. The length of a copper wire is 5 metre and its radius is 1 millimetre a force of 31.4 Newton is applied at each end of the wire.

Q. A LASER is a source of very intense, monochromatic, and unidirectional beam of light. These properties of a laser light can be exploited to measure long distances.The distance of the Moon from the Earth has been already determined very precisely using a laser as a source of light. A laser light beamed at the Moon takes 2.56 s to return after reflection at the Moon’s surface. How much is the radius of the lunar orbit around the Earth ?

Q. Just as precise measurements are necessary in science, it is equally important to be able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity) : (a) the total mass of rain-bearing clouds over India during the Monsoon (b) the mass of an elephant (c) the wind speed during a storm (d) the number of strands of hair on your head (e) the number of air molecules in your classroom.

Q. The unit of length convenient on the nuclear scale is a fermi : 1 f = 10¯¹⁵ m. Nuclear sizes obey roughly the following empirical relation : r = rₒ A⅓ where r is the radius of the nucleus, A its mass number, and ro is a constant equal to about, 1.2 f. Show that the rule implies that nuclear mass density is nearly constant for different nuclei. Estimate the mass density of sodium nucleus. Compare it with the average mass density of a sodium atom obtained in Exercise. 2.27.

Q. The unit of Stefan's constant $\sigma$ is

1. $W{m}^{-2}{K}^{-1}$
2. $W{m}^2{K}^{-4}$
3. $W{m}^{-2}{K}^{-4}$
4. $W{m}^{-2}{K}^4$

Q.

The __________ was adopted by the General Conference of Weights and Measures in 1960 to confirm the uniformity in measurement.

Q. 101.If X, y, z be the distance described by a particle during the p , q, r th second respectively, . Prove that ::: (q-r)X + (r-p)y+ (p-q)z =0

Q. To form a system of units, we require a minimum of 3 physical quantities.

1. False
2. True

Q. The SI unit of universal gas constant (R) is

1. Watt $K^{-1}mo{l}^{-1}$
2. Newton $K^{-1}mo{l}^{-1}$
3. Joule $K^{-1}mo{l}^{-1}$
4. Erg $K^{-1}mo{l}^{-1}$

Q. 10.Take the effect of bulging of the earth and its rotation in account. Consider the following statements (A) there are points outside the earth where the value of g is equal to its value at the equator. (B) there are points outside the earth where the value of g is equal to its value at the poles. 1. Both A and B are correct 2. A is correct but B is wrong 3. B is correct but A is wrong 4. Both A and B are wrong

Q. Select the pair whose dimensions are same

1. Pressure and stress
2. Stress and strain
3. Pressure and force
4. Power and force

Q. 57.A tuning fork gives 4 beats with 50 cm length of sonometer wire. If the length of the wire is shortened by 1 cm, the number of beats is still the same. The frequency of the fork is ?

Q. If force, time and velocity are treated as fundamental quantities, then dimensional formula of energy will be

1. $\left[FTV\right]$
2. $\left[F{T}^{2}V\right]$
3. $\left[FT{V}^2\right]$
4. $\left[F{T}^2{V}^2\right]$

Q.

Why G is called a universal constant.?

Q. If the units of velocity of light C Gravitational constant G and plancks constant h are taken as fundamental units, the dimensional formula for mass in the new system will be?

Q. When a force is applied on a wire of uniform cross- sectional area 3 x 10-6 m2 and length 4 m, the increase in length is 1 mm. Energy stored in it be (Y -2x 1011 N/m2) (1) 6250 J will (2) 0.177J (4) 0.150 J (3) 0075 J

Q. From the dimensional consideration, which of the following equation is correct

1. T = $2\pi \sqrt{\frac{R^3}{GM}}$
2. T =2$\pi \sqrt{\frac{GM}{R^3}}$
3. T =2$\pi \sqrt{\frac{GM}{R^2}}$
4. T =2$\pi \sqrt{\frac{R^2}{GM}}$

Q.

S.I. unit of universal gas constant is

1. cal/°C

2. 

3. J/kg

4. J/mol

Q. Q: what is instantaneous velocity, instantaneous acceleration, instantaneous power ?

Q. The current voltage relation of diode is givenby I = (e^{500/T}- 1) mA, where the applied V is in volts and the temperature T is in degree kelvin. If a student makes an error measuring\underset-+ 0.02 V while measuring the current of 7 mA at 200 K, what will be the error in the value ofcurrent in mA?(A) 0.4 mA(C) 0.5 mA(В)0.04m(D) 0.05 mA0