Introduction

In this science experiment, we will learn to compare the pressure exerted by an iron on fine sand while resting on its three different positions and calculate the pressure exerted in the three cases.

Pressure

1. Upthrust is the force which is acting on an object perpendicular to the surface.
2. Pressure is the thrust per unit area.
Pressure = Thrust/Area.
3. N/m^2 or Pascal is the SI unit of pressure.

Aim

To compare the pressure exerted by an iron on fine sand while resting on its three different positions and calculate the pressure exerted in the three cases.

Apparatus Required

1. Solid iron,
2. Spring balance,
3. Trough filled with fine sand,
4. Stand,
5. Wooden sheet,
6. Temporary marker,
7. Scale

Theory

The force applied per unit area is pressure.

Pressure = Force/Area.

Procedure

Step 1. Mark the dimension of a cardboard sheet with the help of a scale. Name it L, B, H.

Step 2. With the help of spring balance measure the weight of solid.

Step 3. With the help of a wooden sheet level the surface of fine sand in a trough.

Step 4. Place the iron on fine sand with the side L X B.

Step 5. Look at the depression that occurs in the sand.

Step 6. With the help of a marker, mark the height of sand on iron and note it.

Step 7. Remove the iron from the sand, measure its height from the base, and name it a.

Step 8. Level the sand and repeat steps 5, 6 and 7 with side B X H and side L X H and name b,c.

Step 9. Do the above steps two more times.

Observation

1. Least count of spring balance= …….
2. Zero error of spring balance = …..

3. Length of iron = …… m.
4. Breadth of iron= ……m.
5. Height of iron = …….m.

Table 1: Measurement of the weight of iron.

Mean weight of iron = (W’1 + W’2 + W’3 )/3 g wt.

Table 2: Measurement of mark on the cuboid

Calculations

a.

Widest base = …….m

Upright = ………m

Side base = ………m

1. Force exerted by the iron on sand = weight of the iron = kg
2. Calculation of pressure exerted by iron in three cases.

Pressure = Force / Area

For the widest base face, P1 = F / (L X B) N/m^2.

For the Upright face, P2 = F / (B X H) N/m^2 .

For the side base, P3 = F / (L X H) N/m^2.

Precautions

1. Spring balance should be error-free.
2. Carefully measure the zero error of spring balance.
3. While taking the reading of spring balance, eyes should be kept horizontally.
4. Sand must be loose.
5. Keep the iron on the sand gently.
6. Carefully take out the iron from the sand.
7. There should be a proper leveling of sand after every use.

Result

From the marking, we have seen that the thrust on iron in an upright position is greater than the thrust on iron in the widest base or side base position.

For the widest base position, P1 = …….. N/m^2.

For the Upright position, P2 = ………. N/m^2.

For the side base position, P3 = ………..N/m^2.

Observation

In this way, we have seen that the greater the area, the smaller the pressure will be.

Viva Questions With Answers

Q.1 What is the relation between force and pressure?

ANS. Pressure is directly proportional to the force.

Q.2 How does the area depend on pressure?

ANS. Pressure is inversely proportional to area.

Q.3 Name the SI unit of pressure?

ANS. Newton/metre^2 or Pascal.

Q.4 Describe a difference between Force and Pressure.

ANS. Force applied on any body is equal to the body’s weight, while pressure is the force applied on the body per unit area.

Q.5 Why does the wider strip of the school bag feel less weightless on our shoulders as compared to thinner strips?

ANS. Because the greater the area, the less pressure there will be.

Q.6 On whose name the unit pascal is given to pressure?

ANS. Blaise Pascal

Q.7 What was the aim of our experiment?

ANS. To compare the pressure exerted by iron on fine sand while resting on its three different positions and calculate the pressure exerted in the three cases.

Q.8 In what position have you measured the pressure less?

ANS. Widest base position.

Vikram Sarabhai

An Indian physicist and astronomer.