In a world without friction, which of the following activities could you do (or not do)? Explain your reasoning. (a) Drive around an unbanked highway curve; (b) jump into the air; (c) start walking on a horizontal sidewalk; (d) climb a vertical ladder; (e) change lanes while you drive.
Solution 12DQ a) Drive around an unbanked highway curve: You can’t drive through the unbanked highway as there is no friction. Friction also provides the normal reaction, otherwise you would not be able t stand on a train as it is moving. Here the normal reaction is by the friction which holds you. Without friction, any type of motion which includes contact of two objects can’t be done. b) jump into the air: You can jump into air any time. It does not require friction at all. The only thing is you won’t feel the air friction at all. Otherwise it’s completely fine to do this. c) start walking on a horizontal sidewalk: You won’t be able to walk through this. Because it requires the contact of your foot and the surface of sidewalk. If there will not be any friction, you will slip from there with an enormous speed. No force will be there to stop you from slipping. d) climb a vertical ladder: Intuitively you may climb, but still see, there is no friction and the contact force of your foot and the ladder is required. So, you will not get the normal reaction. Without normal reaction, it is impossible to climb the ladder. e) change lanes while you drive: This also you can’t do. The changing of lanes requires a contact force of the wheels of the car and the road. Without this force you are not allowed to change a lane.