Physics 111 Exam 2 and part of 3 Review

Practice Problem 1: A prankster drops a water balloon from the top of a building. If the balloon is traveling at 24.3 m/s when it strikes the ground, how tall is the building? Neglect air resistance.

PE + KE = PE + KE Mgh + 0 = 0 + .5mv^.5 H = v^2 / 2g = 30 meters Solution: PE + KE = PE + KE Mgh + 0 = 0 + .5mv^.5 H = v^2 / 2g = 30 meters

Practice 2: At a certain instant, a compact disc is rotating at 340 rpm (revolutions per minute). What is its angular speed?

Solution: W = 340 * 2pie / 60 = 35 rad/s

Practice Problem 3 When a fan is turned off, its angular speed decreases from 14 rad/s to 7.8 rad/s in 2.0 s. What is the magnitude of the average angular acceleration of the fan?

Solution: W= wi + at 14-7.8 / 2= 3.1 rad/s^2

MOREEEEEEEEEEE PROBLEMMMSS A 34-N force is exerted on a lever at a point 0.20-m from the supporting hinge. The angle between the lever and the force is 40 deg as shown in the figure. What is the torque applied to the lever?

Solution T = Fr sin degree 34 * .2 sin 40 5.1 Nm

Exam 3 material Water flows out of a large reservoir with a diameter of 34.2 m through a narrow pipe 12.0 m below the surface. What is the speed of the water as it comes out of the pipe?

Solution: V=2gh^.5 V=2 ( 9.81)(12)^.5 V= 15.3 m/s

EVEN MORE A disk, a hoop, and a solid sphere are released at the same time at the top of an inclined plane. They all have equal masses and radii and roll without slipping. In what order do they reach the bottom?

Larger inertia = slower movement Sphere, disk, hoop Solution: Larger inertia = slower movement Sphere, disk, hoop