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MDCAT
Physics
2012

Physics · Dawn of Modern Physics

Work through this past-paper style MCQ, then read the full explanation. Practice more physics questions on mMCQ with adaptive practice and topic analytics.

Question

If ‘m’ is the mass, ‘c’ is the velocity of light and x = mc2, then dimensions of ‘x’ will be:

Options
  • A

    [LT-1]

  • B

    [ML2T-2]

  • C

    [MLT-1]

  • D

    [MLT-2]

Explanation

The equation x = mc² represents the relationship between mass and energy, where x is the energy equivalent of a mass m, and c is the speed of light.

To determine the dimensions of x, we need to consider the dimensions of each variable in the equation. The dimensions of mass are [M], the dimensions of the speed of light are [LT-1].

Using the rules of dimensional analysis, we can find the dimensions of x by substituting the dimensions of m and c into the equation and simplifying:

x = mc²

= [M][LT-1]²

= [M][L2T-2]

Therefore, the dimensions of x are [ML2T-2], which is option B. 

This option is incorrect because the dimensions of x = mc2 are not [LT-1]. The dimension [LT-1] represents inverse time, which is not applicable here. 

The equation x = mc² represents the relationship between mass and energy, where x is the energy equivalent of a mass m, and c is the speed of light.

To determine the dimensions of x, we need to consider the dimensions of each variable in the equation. The dimensions of mass are [M], the dimensions of the speed of light are [LT-1].

Using the rules of dimensional analysis, we can find the dimensions of x by substituting the dimensions of m and c into the equation and simplifying:

x = mc²

= [M][LT-1]²

= [M][L2T-2]

Therefore, the dimensions of x are [ML2T-2], which is option B.

This option is incorrect because the dimensions of x = mc2 are not [MLT-1]. The dimension [MLT-1] represents momentum per unit time, which is not the correct dimension for x = mc2. 

This option is incorrect because the dimensions of x = mc2 are not [MLT-2]. The dimension [MLT-2] represents force per unit area, which is not relevant to the expression x = mc2. 

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Tagged under Physics · Dawn of Modern Physics · 2012