# Physics 107 Midterm Exam 2

What is the equation for angular acceleration, α, when θ is the angle, ω is the angular velocity, and t is the time?
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The clockwise rotation of an object produces negative angular velocity. Therefore, when the object is slowing down and rotating clockwise, the angular acceleration is positive.

In a circular motion, the clockwise rotation of the object produces negative angular velocity. Therefore, for an object which is slowing down and rotating, clockwise would have a positive angular acceleration.
Two different size boxes made of the same material are located on a flat surface. If Box A has been filled so that it only has ⅓ the mass of Box B, but it has twice the bottom surface area what is the relationship between the forces that must be used to overcome the friction generated by each box to move them parallel along the floor?
Box B requires 3 times as much force to overcome friction. Static friction only depends on the coefficient of static friction and the normal force which is calculated as N = mg in this situation.

Static friction is calculated as fsmax = μsN, meaning that it only depends upon the two materials in contact (the coefficient of static friction) and the weight of the box on the flat surface (the normal force). Surface area does not impact friction.
...supplies the centripetal force and is numerically equal to it. Centripetal force is perpendicular to velocity and causes uniform circular motion. The larger the Fc, the smaller the radius of curvature size r and the sharper the curve. The second curve has the same v, but a larger Fc produces a smaller r'.

Fc=(mv^2)/r