Apaper 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?

Mechanical(ME) energy, in physical sciences, is the sum of kinetic energy (KE) and potential energy (PE). Below are the calculation in obtaining the energies,
 
     (1) KE =   0.5mv²     =  0.5(0.1 kg) x (2 m/s)² = 0.2 J
     (2) PE =    md          = (0.1 kg) x (1.5 m)        = 0.15 J
      (3) ME =  KE + PE = 0.2 J + 0.15 J               = 0.35 J

Thus, the mechanical energy is 0.35 Joules.