Q1. Stationary bicycle is raised off the ground, and its front wheel (m = 1.3 kg) is rotating at an angular velocity of 12.0 rad/s (see the drawing). The front brake is then applied for 3.0 s, and the wheel slows down to 3.8 rad/s. Suppose that all the mass of the wheel is concentrated in the rim, radius of which is 0.31 m. The coefficient of kinetic friction between each brake pad and the rim is μk = 0.85. What is the magnitude of the normal force that each brake pad applies to the rim?
Q2. An alpha particle (m = 6.7 ´ 10-27 kg, q = +3.2 ´ 10-19 C) has a speed of 20 km/s at point A and moves to point B where it momentarily stops. Only electric forces act on the particle throughout this motion. Find out an electric potential difference VA - VB.