The setup alongside shows four metal bolts with different number of windings on each. The windings (wires) are connected to a
power source.
6.1 What is this setup known as?
6.2 Which one of the four bolts will have the biggest (strongest) effect?
6.3 To which main requirement must the wire, which is turned around
the bolt comply?​

It's a snowy day and you're pulling a friend along a level road on a sled. you've both been taking physics, so she asks what you think the coefficient of friction between the sled and the snow is. you've been walking at a steady 1.5m/s, and the rope pulls up on the sled at a 32 ∘ angle. you estimate that the mass of the sled, with your friend on it, is 65 kg and that you're pulling with a force of 80 n .