# The efficiency of the inclined plane is 40%. When lifting a load on it, we performed work of 400 J.

The efficiency of the inclined plane is 40%. When lifting a load on it, we performed work of 400 J. What is the useful work in this process? The mass of the Zhiguli car is 900 kg, and the contact area of the tire with the road is 225 cm3. How much pressure does the car put on the road?

Efficiency = 40%.

Az = 400 J.

Ap -?

The efficiency coefficient shows what part of the spent work Az goes into useful Ap, expressed as a percentage.

Efficiency = Ap * 100% / Az.

Ap = Az * efficiency / 100%.

Ap = 400 J * 40% / 100% = 160 J.

Answer: the useful work is Ap = 160 J.

m = 900 kg.

g = 9.8 m / s2.

S = 225 cm2 = 0.0225 m2.

P -?

P = F / S.

F = m * g.

P = m * g / S.

P = 900 kg * 9.8 m / s2 / 0.0225 m2 = 392000 Pa.

Answer: the car puts pressure on the road P = 392000 Pa.

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