A car weighing 10 ^ 3 kg accelerates from rest relative to the ground to a speed of 72 km / h.

| April 26, 2021 | education

A car weighing 10 ^ 3 kg accelerates from rest relative to the ground to a speed of 72 km / h. Calculate the useful work A1 performed by the car engine in the reporting system connected to the Earth and the work A2 in the reporting system associated with the second car moving at a constant speed of 72 km / h towards the first.

Task data: m (vehicle weight) = 103 kg; acceleration from rest; V1 (required speed) = 72 km / h (20 m / s); V2 (speed of oncoming vehicle) = 72 km / h (20 km / s).

1) The first work of a car engine (reference system – Earth): A = ΔEk1 = m * V1 ^ 2/2 – 0 = 10 ^ 3 * 20 ^ 2/2 = 200 kJ.

2) The second work of the car engine (reference system – the second car): A = ΔEk1,2 = m * V1,2 ^ 2/2 – 0 = m * (V1 + V2) ^ 2/2 = 10 ^ 3 * (20 + 20) ^ 2/2 = 800 kJ.



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