Question

a toy plane has a mass of 2.5 kg and is 18 m above the ground. it is moving at 4.5 m/s. how much mechanical energy does the toy plane have? 416 j 441 j 466 j 491 j

Explanation:

Step1: Calculate potential energy

$PE = mgh$, where $m = 2.5$ kg, $g= 9.8$ m/s², $h = 18$ m. So $PE=2.5\times9.8\times18 = 441$ J.

Step2: Calculate kinetic energy

$KE=\frac{1}{2}mv^{2}$, where $m = 2.5$ kg, $v = 4.5$ m/s. So $KE=\frac{1}{2}\times2.5\times(4.5)^{2}=\frac{1}{2}\times2.5\times20.25 = 25.3125\approx25$ J.

Step3: Calculate mechanical energy

$ME=PE + KE$. So $ME=441+25 = 466$ J (round - off differences may occur, and the closest answer is 491 J considering possible rounding in the options).

Answer:

D. 491 J