Answer:
Step-by-step explanation:
The precautions are
1) The angle of displacement of the bob should be small
2) The pendulum should be oscillated in a vertical plane only
3) Fans should be switched off to control draught
4) The pendulum should oscillate freely
5) Parallax error should be avoided when taking readings
6) Zero error should be avoided when using the stop watch
7) The readings should be repeated at least 3 times to ensure accuracy of the result
8) When measuring the length of the pendulum, it should be done from the center of mass of the plumbob
9) The top support to which the pendulum is anchored should be fixed.