Tag: physics

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Questions Related to physics

Multiple choice physics energy and its forms idea of energy introduction to work and energy work and energy

The negative of the work done  by the conservative internal forces on a system equals to the change in 

  1. total energy

  2. Kinetic energy

  3. Potential energy

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

The negative of the work done  by the conservative internal forces on a system equals to the change in potential energy


Hence, correct answer is option $C$

Multiple choice physics energy and its forms idea of energy introduction to work and energy work and energy

The unit of work is joule $(J)$ in the $SI$ system and erg in the $CGS$ system. Find number of ergs in $1\ joule$.

  1. $10^{17} ergs$.
  2. $10^{9} ergs$.
  3. $10^{8} ergs$.
  4. $10^{7} ergs$.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In the SI system, 1 Joule = 1 kg * m^2 / s^2. In the CGS system, 1 erg = 1 g * cm^2 / s^2. Since 1 kg = 10^3 g and 1 m^2 = 10^4 cm^2, 1 J = 10^3 * 10^4 = 10^7 ergs.

Multiple choice physics energy and its forms idea of energy introduction to work and energy work and energy

Work done charge of mass 2 Kg due to external force against electrostatics force is - 10 J if charge is displaced from A to B. Velocity of charge at point A is 4m/s and at B is 2m/s then find difference is electropotential energy $ (U _s - U _A) $

    • 10J
    • 10J
    • 21J
    • 2J
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

By the work-energy theorem, the total work done equals the change in kinetic energy. The work done by the external force is -10 J. The change in kinetic energy is 1/2 * m * (v_B^2 - v_A^2) = 1/2 * 2 * (4 - 16) = -12 J. The change in potential energy is the negative of the work done by the conservative (electrostatic) force. Given the total work W_ext + W_elec = Delta K, we find Delta U = +10 J.

Multiple choice physics energy and its forms idea of energy introduction to work and energy work and energy

Define the term calorie. How is it related to joule ?

  1. The amount of energy requires to raise the temperature of 1 gram of water by 1° Celsius, 1 Cal = 4.18 J
    <a href="http://scienceworld.wolfram.com/physics/Celsius.html&quot;&gt;&lt;/a>

  2. The amount of energy requires to raise the temperature of 1 gram of water by 1 Kelvin, 4.18 Cal = 1 J

  3. The amount of energy requires to raise the temperature of 1 gram of water by 1 Fahrenheit, 4.18 Cal = 1 J

  4. The amount of energy requires to raise the temperature of 1 gram of ether by 1° Celsius, 1 Cal = 4.18 J
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The term calorie can be defined as the energy needed to raise the temperature of 1 gram of water by $ 1$ °C. 
$1 \ cal = 4.18 \ J$