Hello! Yesyerday I saw a bycicle which had attached to its back a box on wheels. Supposing that the coeficient of friction is the same as the coeficient of friction at the surface between bike`s wheels and ground, what of the 2 following cases is worser for the cycler ( he has to make more effort) : 1. The box is 6 kg mass. 2. There is no box and the cycler is heavier than initial with 6 kg. Thanks you!!