Answer:
A)3.8196 *
Newtons B) 2.153 *
Newtons
Explanation:
Force = Pressure * Area.
Pressure is given as 120GPa
Area = Cross Sectional Area of Rod = Area Of A circle = π
.
Area Expansivity β = 
Area Expansivity β = 2α
α = 16.9x10-6/ ° C.
Radius of Rod AB = Half 0f Diameter, 200mm =
= 0.1 m
Radius of Rod BC = Half Of Diameter, 150mm =
= 0.075 m.
Note: To convert from millimeter to meter you divide by 1000.
Area of Rod AB = π *
= 0.0314
Area of Rod BC = π *
= 0.0177
.
Change in Area = 2α * Original Area * Temperature Rise. Therefore for
Rod AB = 2 * 16.9*
* 0.0314 * 30 = 3.183 * 
.
For Rod BC we have = 2 * 16.9*
* 0.0177 * 30 = 1.794∈-5
.
The forces on each rods will be given by.
Force AB = Pressure * Area of Rod AB
= 120GPa * 3.183 *
gives 3.8196 *
Newtons.
Force BC = Pressure * Area of Rod BC
= 120GPa * 1.794 *
gives 2.153 *
Newtons