有一質量1450KG的中型轎車在水平高速公路上需要40匹馬力以維持時速108公里的速率，求:(1)轎車引擎的推力?(2)假設轎車所受的空氣阻力和摩擦力不變，並以相同速率開上傾角7度的斜坡，計算轎車引擎的輸出功率?

(1A) F = ?

v = 108 kph / 3.6 mps/kph = 30 m/s

F = 746*hp/v*g

= 746*40/30

= 995 N / 9.8 N/kg

= 101.5 kg



(1B) HP = ?

= hp*cosQ

= 40*cos7

= 39.7 horse powers




(2) E = ?

= mg*L*sinQ

= 15*9.8*100*sin15

= 3805 J




(3) f = ?

E1 = mg*L*sinQ

E2 = m*v^2 / 2

E2 = mg*cosQ*f*L

E1 = E2 + E3

=> f = (E1 - E2)/mg*L*cosQ

= (g*L*sin30 - 0.5v^2)/g*L*cos30

= (9.8*2.5 - 0.5*16) / 9.8*5*0.866

= 0.389