Question

(1) After landing on an unfamiliar planet, a space explorer constructs a simple pendulum from a massless rod of length 50.0 cm. The bob mass is 0.20 Kg. (Reminder: a "bob" is the mass on the end of the pendulum.) The bob is pulled from the vertical by an angle of 5° and released. The pendulum executes 100 complete cycles in 163 s. (a) What is the gravitational strength g at that location on the planet? (10 points) (b) What is the maximum speed of the bob and how much time does it take for the bob to reach its maximum speed ? [hint: remember that the unit for the absolute value of an angle is radians.] (15 points) (c) The bob mass is now doubled to 0.40 Kg and is released from an angle of 10°. Now what is the maximum speed and how long does it take the bob to reach this speed? (6 points)
***So my question is why did my professor divide by 4 at the end of part b? Please explain and show work if possible.

Answer 1

At T/4 the velocity is maximum because the bob is at the lowest position of the pendulum when string makes 0 degree with vertical. At lowest position the gravitational potential energy is minimal and kinetic energy is maximum.

At T/4 the velocity is maximum because the bob is at the lowest position of the pendulum when string makes 0 degree with vertical. At lowest position the gravitational potential energy is minimal and kinetic energy is maximum. This is the movement of bob is pendulum. It is released when the angle is 5 degree from vertical. Let's take snapshot of each motion