An object of weight 20n attached at the end of a spring

Question

1. What is gravity.
2. define the centre of gravity and state why buses with loads on topare likely to fall.
3. An object of weight 20N attached at the end of a spring causes an extension of 0.5cm on the spring.

a) Determine the spring constant

b) Determine theweight of an object that could cause an extension of 0.86cmwhen attached at the end of the same spring