Alfred's antics again
One day, Alfred wanted to show off to his elder sister, Brenda, how powerful his motorbike was. He rode his motorbike with Brenda riding pillion and accelerated from rest to in 3 seconds. If the total mass of Alfred, his motorbike and Brenda is 400 kg and his motorbike engine exerts a constant driving force of 4000 N, find the average resistive force in Newtons.
The answer is 800.
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1 solution
The total momentum would be 4 0 0 k g ∗ 2 4 m / s = 9 6 0 0 k g m / s . The resultant force is therefore 3 s 9 6 0 0 k g m / s = 3 2 0 0 k g m / s 2 = 3 2 0 0 N . With a driving force of 4000 N, we can calculate the resistive force to be 4000-3200=800 N.