Tag: physics

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Questions Related to physics

Multiple choice physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

A positron is emitted from $\mathrm{N}\mathrm{a} _{11}^{23}$. The ratio of the atomic mass and atomic number of the resulting nuclide is

  1. $22/10$
  2. $22/11$
  3. $23/10$
  4. $23/12$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When a positron is emitted from nucleus, proton will convert into a neutron. So atomic number will be decrease by one  but atomic mass will be constant. 

Thus, atomic mass / atomic number $=23/(11-1)=23/10 $

Multiple choice physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

Masses of two isobars $ _{29}^{64}\textrm{Cu}$ and $ _{30}^{64}\textrm{Zn}$ are $63.9298 amu$ and $63.9292 amu$ respectively. It can be concluded from these data that 

  1. Both the isobars are stable
  2. $^{64}Zn$ is radioactive, decaying to $^{64}Cu$ through $\beta -$ decay
  3. $^{64}Cu$ is radioactive, decaying to $^{64}Zn$ through $\lambda -$ decay
  4. $^{64}Cu$ is radioactive, decaying to $^{64}Zn$ through $\beta -$ decay
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Since mass of the isobar has decreased, an electron has been ejected.

Thus $^{64} _{29}Cu$ decays to $^{64} _{30}Zn$ through the $\beta - $ decay as-
$^{64} _{29}Cu\rightarrow^{64} _{30}Zn+^{0} _{-1}e$

Multiple choice physics floatation buoyancy fluid pressure option b: engineering physics

When a solid is completely immersed in a fluid, the apparent loss of weight of solid is _______ volume of fluid displaced 

  1. more than

  2. less than

  3. equal to

  4. cant say
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

From the principle of Archimedes, loss of weight is equal to the weight of the liquid displaced.

Multiple choice physics floatation buoyancy fluid pressure option b: engineering physics

When a body is fully immersed in a liquid the apparent loss in the weight of body is equal to :

  1. volume of liquid displaced by the body

  2. density of the liquid

  3. weight of liquid displaced by the body

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Archimedes principle, the weight of water displaced is equal to the weight of immersed part.For a solid floating in a liquid, its weight acting vertically down at its centre of gravity is equal to the weight of the liquid displaced by the immersed part of the solid acting vertically up at its centre of buoyancy. In the floating condition, the apparent weight and the apparent density of the solid are zero and the body is said to be weightless.

Multiple choice physics floatation buoyancy fluid pressure option b: engineering physics

State whether the weight of an iron sinker with cork combined in water will be more or less than that of the iron sinker alone in water. 

  1. Less

  2. More

  3. Same

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The weight of an iron sinker with cork combined in water will be less than that of the iron sinker alone in water.
This is because upthrust on cork due to water (when completely immersed) is greater than its weight.

Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

An incompressible liquid of density $\rho$ is contained in a vessel of uniform cross-sectional area $A$. If then atmospheric pressure is $p$, then the force acting on a horizontal plane of area a situated at a depth $d$ in liquid is given by

  1. $Ap+apgd$
  2. $\dfrac { p }{ A } +\dfrac { \rho gd }{ a }$
  3. $\dfrac { p+\rho gd }{ a }$
  4. $a\left( \rho\ gd+p \right)$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The pressure at depth d is P = p + rho*g*d. Force is pressure times area. Thus, F = P * a = (p + rho*g*d) * a = a(p + rho*g*d).

Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

A gas is enclosed in a rectangular vessel. $20 \times 10^23$ molecules of the gas strike a well of the vessel normally per second, with a velocity of 250m/s and rebound with the same speed in the opposite direction. What is the force exerted by the gas on the wall if the mass of each molecule is $5 \times 10^-23$ g ? 

  1. 50 N

  2. 40 N

  3. 75 N

  4. 25 N
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Force = change in momentum per unit time. Delta p = m * v - (m * -v) = 2mv. Force = N * (2mv) / t. Given N/t = 20 * 10^23 molecules/s, m = 5 * 10^-26 kg (converting 5 * 10^-23 g), v = 250 m/s. F = 20 * 10^23 * 2 * 5 * 10^-26 * 250 = 20 * 10^23 * 10^-25 * 250 = 20 * 0.1 * 250 = 50 N.