A 0.80-kg object tied to the end of a 2.0-m string swings as a pendulum. At the lowest point of its swing, the object has a kinetic energy of 10 J. Determine the speed of the object at the instant when the string makes an angle of 50° with the vertical.
A) 5.6 m/s
B) 4.4 m/s
C) 3.3 m/s
D) 5.0 m/s
E) 6.1 m/s

Question

Quizplus · Accepted Answer

At the lowest point, all energy is kinetic: KE = 10 J. At 50°, some energy is potential: PE = mgh = 0.80 * 9.8 * (2 - 2cos50°). Subtract PE from 10 J to find remaining KE, then use KE = 0.5 * m * v^2 to solve for v.

A 080-Kg Object Tied to the End of a 2