Answer:
Part a)
![dF = -(mv^2)/(r^2) dr](https://img.qammunity.org/2020/formulas/physics/high-school/584buzl6aelq0cs2pjk9jdv9cw57zci2fv.png)
Part b)
![dF = (2mvdv)/(r)](https://img.qammunity.org/2020/formulas/physics/high-school/anahwqak4ryh9emnrj5p35dotvycui9ci4.png)
Part c)
![dT = - (2\pi r)/(v^2) dv](https://img.qammunity.org/2020/formulas/physics/high-school/nceclm3i31qw7l5kmsj975646a11xf3x3r.png)
Step-by-step explanation:
Part a)
As we know that force on the passenger while moving in circle is given as
![F = (mv^2)/(r)](https://img.qammunity.org/2020/formulas/physics/high-school/6foq74gyemvmnrkn6vrvp4c8invf25tbbe.png)
now variation in force is given as
![dF = -(mv^2)/(r^2) dr](https://img.qammunity.org/2020/formulas/physics/high-school/584buzl6aelq0cs2pjk9jdv9cw57zci2fv.png)
here speed is constant
Part b)
Now if the variation in force is required such that r is constant then we will have
![F = (mv^2)/(r)](https://img.qammunity.org/2020/formulas/physics/high-school/6foq74gyemvmnrkn6vrvp4c8invf25tbbe.png)
so we have
![dF = (2mvdv)/(r)](https://img.qammunity.org/2020/formulas/physics/high-school/anahwqak4ryh9emnrj5p35dotvycui9ci4.png)
Part c)
As we know that time period of the circular motion is given as
![T = (2\pi r)/(v)](https://img.qammunity.org/2020/formulas/physics/high-school/qv3lhy8w67s1v34qhm2h4vjwzqhtztogyz.png)
so here if radius is constant then variation in time period is given as
![dT = - (2\pi r)/(v^2) dv](https://img.qammunity.org/2020/formulas/physics/high-school/nceclm3i31qw7l5kmsj975646a11xf3x3r.png)