JEE MAIN - Physics (2019 - 11th January Evening Slot - No. 12)
If speed (V), acceleration (A) and force (F) are considered as fundamental units, the dimension of Young,s modulus will be:
V$$-$$2A2F2
V$$-$$4A$$-$$2F
V$$-$$4A2F
V$$-$$2A2F$$-$$2
Explanation
We know,
Young's modulus (Y) = $${{{F \over A}} \over {{{\Delta l} \over l}}}$$
$$ \therefore $$ [Y] = $${{\left[ {ML{T^{ - 2}}} \right]} \over {\left[ {{L^2}} \right]}}$$ = [ ML-1T-2]
Let [Y] = [V]x [A]y [F]z
$$ \therefore $$ [ ML-1T-2] =
[LT-1]x [LT-2]y [MLT-2]z
$$ \Rightarrow $$ [ ML-1T-2] =
[ Mz Lx + y + z T-x -2y - 2z
For dimensional balance, the dimension on both sides should be same.
So, z = 1
x + y + z = -1
$$ \Rightarrow $$ x + y = -2 ........(1)
and -x -2y - 2z = -2
$$ \Rightarrow $$ x + 2y = 0 ...........(2)
By solving those two equations we get,
x = -4 and y = 2
$$ \therefore $$ [Y] = V$$-$$4A2F1
Young's modulus (Y) = $${{{F \over A}} \over {{{\Delta l} \over l}}}$$
$$ \therefore $$ [Y] = $${{\left[ {ML{T^{ - 2}}} \right]} \over {\left[ {{L^2}} \right]}}$$ = [ ML-1T-2]
Let [Y] = [V]x [A]y [F]z
$$ \therefore $$ [ ML-1T-2] =
[LT-1]x [LT-2]y [MLT-2]z
$$ \Rightarrow $$ [ ML-1T-2] =
[ Mz Lx + y + z T-x -2y - 2z
For dimensional balance, the dimension on both sides should be same.
So, z = 1
x + y + z = -1
$$ \Rightarrow $$ x + y = -2 ........(1)
and -x -2y - 2z = -2
$$ \Rightarrow $$ x + 2y = 0 ...........(2)
By solving those two equations we get,
x = -4 and y = 2
$$ \therefore $$ [Y] = V$$-$$4A2F1
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