Question #116760

a car has a drag coefficient Cd=0.30, a frontal area of A = 1.9 meter square, a mass 1.2 tonnes and a coefficient of rolling resistance, Cr,= 0.012. it is travelling up a hill with a slope of 1 in 20 at 110 kph.

at what rate it is doing work against gravity(i.e. at what rate is it increasing its gravitational potential energy)?

Pg=_______kW.

(a 1:20 grade means that it rises 1m for every 20 m travelled along the road: sin(theta) = 1/20.)

at what rate it is doing work against gravity(i.e. at what rate is it increasing its gravitational potential energy)?

Pg=_______kW.

(a 1:20 grade means that it rises 1m for every 20 m travelled along the road: sin(theta) = 1/20.)

Expert's answer

"P_g=\\frac{\\Delta mgH }{\\Delta t}=mg\\frac{\\Delta H}{\\Delta t}" as "\\Delta H=v(\\sin \\theta) \\Delta t" then "P_g=mgV\\sin\\theta\\approx1.2\\sdot10^3\\sdot9.8\\sdot110\\sdot3.6\\sdot0.05\\approx"

"\\approx232.8\\sdot10^3=233kW"

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