Answer:
Force = 7.3 kN
Explanation:
Elastic Modulus = Stress / Strain
Since the maximum stress applied can be 90 MPa, lets check the corresponding maximum strain using the above equation.
70 * 10^9 = 90 * 10^6 / Strain
Strain = 0.0012857
Strain = Change in length/total length
Change in Length = 0.0012857 * 2.5
Change in Length = 0.003214 m
Converted to mm this is: 0.003214 * 1000 = 3.214 mm
Thus we can see that strain is the limiting factor, and not stress. This is because with the maximum stress possible applied, we go over the strain limit.
Doing another quick calculation, we can take out the maximum stress with strain equal to 3mm/2.5m
Strain = (3/1000)/2.5
Strain = 0.0012
Modulus of elasticity = Stress/ Strain
Stress = 70 * 10^9 * 0.0012
Stress = 84 MPa
This stress is under both the strain and stress limit.
Taking out the force due to this stress:
Stress = force / area
Force = 84 * 10^6 * Area
Force = 84 * 10^6 * (25/1000) * (35/1000)
Force = 7350 N or 7.3 kN
