What is the minimum coefficient of friction required to maintain pure rolling motion for the disk?

What is relative velocity? in which condition is relative velocity known by adding the velocity of the first body and that of the second body

Very large accelerations can injure the body, especially if they last for a considerable length of time. one model used to gauge the likelihood of injury is the severity index ( ), defined as =/ . in the expression, is the duration of the accleration, but is not equal to the acceleration. rather, is a dimensionless constant that = the number of multiples of that the acceleration is equal to.in one set of studies of rear-end collisions, a person's velocity increases by 13.7 km/h with an acceleration of 36.0 m/s2 . let the + direction point in the direction the car is traveling. what is the severity index for the collision?

Ihave a density of 1.61g/cm^3 and a mass of 28g. find the missing value