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  4. A body of mass m=10-2 kg is moving in a medium and experiences a frictional force F=-kv2. Its initial speed is v0=10 ms-1. If, after 10 s, its energy is (1/8) mv02, the value of k will be :

Q. A body of mass is moving in a medium and experiences a frictional force . Its initial speed is . If, after , its energy is , the value of will be :

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