Question

A paper airplane with mass 0.1 kg is flying 1.5 m above the ground with a speed of 2 m/s. What is the total mechanical energy of the paper airplane?

Answer 1

Total mechanical energy = kinetic energy + potential energy
E = KE + PE
E = ½mv² + mgh
E = ½(0.1 kg)(2 m/s)² + (0.1 kg)(9.8 m/s²)(1.5 m)
E = 0.2 J + 1.47 J
E = 1.67 J

Answer 2

We know that:
EM=Epg+Ek
So:
Epg=mgh
Epg=0,1kg*9,8m/s²*1,5m
Epg=1,47J
Now:
Ek=1/2mv²
Ek=1/2(0,1kg)(2m/s)²
Ek=0,2J
That give us:
EM=1,47J*0,2J
EM=1,67J