Question

A room has dimensions 3m x 4m x 5m. A fly starting at one corner ends up at the diametrically opposite corner. The magnitude of the displacement of the fly is:

• A. 12 m
• B. 60 m
• C. $2\sqrt{5}$ m
• D. $5\sqrt{2}$ m

Answer 1

The correct option is D $5\sqrt{2}$ m

Figure shows the bold line whose length we have to calculate

Using 3D version of pythagoras

$d^2=a^2+b^2+c^2$

$d^2=3^2+4^2+5^2$

$d^2=9+16+25$

$d^2=50$

$d=\sqrt{50}$

$d=5\sqrt{2}m$

Therefore the magnitute of the displacement of the fly is $5\sqrt{2}m$