Question

Once a physicist, always a physicist! Marc can’t even do normal chores without thinking of the physics behind what he is doing (it really is exhausting!). For instance, he was cutting the grass once and he saw a rock of mass m ≈ = 100 g just ahead of his lawnmower. He thought to himself, "since I’m a physicist, I’m no good at any sports, but maybe I can use physics to launch this rock as if I was a famous baseball player!". Marc then positioned the lawnmower such that the very tip of the 50-cm blade (which has a mass of M = 2 kg) would strike the rock as he ran it over.

(a) If the engine was running at 60 rev/s and is now spinning at 55 rev/s (after running over the rock), what is the launch velocity of the rock?

(b) One thing many physicists do is they get too excited about their seemingly fun ideas and forget to think them through. As the rock launched out from under the lawnmower, Marc noticed we was only 10-m away from his house (which was down a bit of a hill) and that the center of his 1-m tall kitchen window was perfectly lined up with the lawnmower. Did Marc just break his window?

Answer 1