The part of the tire on the ground of a moving car is relatively stationary compared to the ground, right? The way the wheels work is the friction parallel to the direction of movement right? So when we calculate centripetal acceleration for cars going in a circle and the friction forces, why do...
Homework Statement
In rotational dynamics, a typical problem would be along the lines of a ring with mass m and radius r rolling down a hill with angle θ to the horizontal. Find the acceleration of the ring.
Homework Equations
Ʃτ=I\alpha = r x (friction)
ƩF = ma = mgsinθ - (friction)...
I've always noticed something strange about new york city subways. When they start to slow down, you feel a force pushing you forward, which seems fine. However, the subway car actually stops, you feel a jerk backward at that moment. Is there an explanation for this?