On complete combustion , a litre of petrol gives off heat equivalent to `3xx10^(7)J` . In a test drive, a car weighing 1200kg, including the mass of driver, runs 15km per litre while moving with a uniform speed on a straight track. Assuming that friction offered by the road surface and air to be uniform, calculate the force of friction acting on the car during the test drive. If the efficiency of the car engine were `0.5.

Explanation

To solve the problem step by step, we will follow these calculations:

### Step 1: Calculate the effective energy produced by the car from 1 litre of petrol.
The heat equivalent from the combustion of 1 litre of petrol is given as \(3 \times 10^7 \, J\). The efficiency of the car engine is given as \(0.5\).

\[ \text{Effective Energy} = \text{Efficiency} \times \text{Heat Equivalent} \]
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