6.1 Define the following terms: 6.1.1 Stress 6.1.2 Strain 6.2 A steel bar experiences a stress of 250 MPa - NSC Technical Sciences - Question 6 - 2020 - Paper 1

Strain is the measure of deformation representing the displacement between particles in a material body. It is defined as the change in length divided by the original length and is expressed as:

where (\Delta L) is the change in length and (L_0) is the original length.

To calculate the strain on the bar, we can use the formula relating stress and strain:

In this case:

• Stress = 250 MPa = 250 \times 10^6 Pa
• Modulus of Elasticity = 190 GPa = 190 \times 10^9 Pa

Substituting:

To calculate the force exerted on the bar, we can use:

First, we need to find the cross-sectional area (A) of the bar:

Then we apply:

An increase in temperature typically results in a decrease in the viscosity of a fluid. This is because higher temperatures provide more energy to the molecules, allowing them to move more freely and overcome the intermolecular forces that contribute to viscosity.

A perfectly plastic body is a type of material that undergoes permanent deformation without any increase in stress beyond a certain yield point. Once this yield point is reached, the material will deform indefinitely under constant stress without returning to its original shape.

1. Clay
2. Mud

Pascal's law states that in a confined fluid at rest, any change in pressure applied at any point in the fluid is transmitted undiminished throughout the fluid in all directions.

Using Pascal's law, we can find the minimum force required:

Given:

• (F_2 = 20000 \ N, A_1 = 0.8 \ m^2, A_2 = 0.05 \ m^2)

Substituting in:

The thrust of a liquid refers to the axial force exerted by the liquid when it flows or is displaced. This force is a result of the pressure exerted by the liquid on the walls of the container or on an object within the liquid.