A simple pendulum is made my attaching a rod of negligible mass to a 2.0 kg pendulum bob at the end. It is observed that on Earth, the period of small-angle oscillations is 1.0 second. It is also observed that on Planet X this same pendulum has a period of 1.8 seconds. How much does the pendulum bob weigh on Planet X? a) 6.2 N
b) 7.0 N
c) 7.8 N
d) 8.6 N
e) 9.4 N

the correct answers is a      W' = 6.2 N

Explanation:

In this exercise they give the description of a simple pendulum, its angular velocity

          w =

angular velocity is related to frequency and period

          w = 2π f = 2π / T

we substitute

          T = 2π \sqrt { \frac{l}{g} }  

          T² = 4π²  

With the period on Earth we can find the length of the pendulum

         l =

         l =

         l = 0.25 m

this longitude is maintained on planet X, so we can find the value of the acceleration of gravity (g ’) on that planet

         g’ =

          g’ =

          g’ = 3.05 m / s²

therefore the weight of the body on this planet is

           W ’= m g’

the mass is invariable in all systems

           W ’= 2.0 3.05

           W ‘= 6.1 N

When examining the correct answers is a

diagram is missing, but i will try to explain your doubt.

answer:

amplitude is the maximum displacement or distance moved on a point of a vibrating body or wave measured from its equilibrium position.it is equal to half the length of vibration path.