Reflection

1. What is pressure?

2. How does force and area affect pressure in solids.

3. Trucks which carry heavy loads have many wheels.Explain.

4. A block of copper of density 8.9g/cm^3, measures 5cm x 3cm x 2cm.Given that the force of gravity is 10N/kg,determine;

(i) the maximum pressure.

(ii) the mimimum pressure that it can exert on a horizontal surface.

Feedback

1. Pressure is force acting normally(perpendicularly) per unit area.

2.Pressure in solids increases with increasing in force applied if area is kept constant while pressure decreases with increasing in area of contact with the surface if force is kept constant.

3. Many wheels increase area in contact with the ground hence decreasing the pressure exerted by the trucks on the ground.

4. (i) maximum pressure=force/minimum area

volume =length x width x volume = 5cm x 3cm x 2 cm = 30cm^3.

mass = density x volume = 8.9 x 30 = 267g, force =267/100 = 2.67N.

Minimum area = 0.02 x 0.03 =0.0006 m^2.

maximum pressure = 2.67/0.0006 = 4450 N/m^2

(ii) Minimum pressure= force/maximum pressure

maximum area = 0.05 x 0.03 = 0.0015m^2.

minimum pressure = 2.67/0.0015 = 1780N/m^2.