class 9 / HOLIDAY HOMEWORK / PHYSICS / EXPERIMENTS

Experiment – 1

Force required to move a wooden block

Our Objective

To establish relationship between weight of a rectangular wooden block lying on a horizontal table and the minimum force required to just move it using a spring balance.

The Theory

According to Newton’s Second Law of Motion, the force acting on a body is directly proportional to the product of the mass of the body and the acceleration produced in the body by the application of the force. The acceleration takes place in the direction in which the force acts.

Newton’s Second Law of Motion precisely explains the relationship between force and acceleration.

Suppose a body of mass ‘m’ is moving by the application of a force ‘F’,  then the produced acceleration ‘a’ will be directly proportional to the applied force.

Acceleration ∝ Force 

F ∝ a 

 F ∝ m 

             Therefore, F = kma     

Materials Required:

Wooden block and spring balance of 5 N.

Procedure:

1. A wooden block with a hook is placed on a table.
2. Note down the least count of the spring balance.
3. The spring balance is attached to the hook.
4. Hold the spring in such a way that the reading displayed in the spring balance can be noted down without any parallax error.
5. The applied force on the spring balance is gradually increased until it just starts to move.
6. The reading of the spring balance is noted.

Observation:

Least count of the spring balance = value of 1 small division = …….g.wt

Trial No;	Mass of the block, M (kg)	Force required, F (N)

As the mass of the block increases the force required to move the block is also increases.

Result:

Force applied to just move the block is directly proportional to the mass of the block.

ie, F ∝ M

Precautions:

1. A suitable spring balance to pull the block must be used.
2. The spring balance should be brought in elastic mode before doing the experiment.
3. The reading of the spring balance should be taken without any parallax error.
4. A smooth table or surface must be used.

Experiment – 2

(Pressure and area relation)

#Our Objective

To observe and compare the pressure exerted by a solid iron cuboid on sand while resting on its three different faces and to calculate the pressure exerted in the three cases. 

#The Theory

To study and compare the pressure exerted by a solid iron cuboid on sand, we need to find its mass and weight.

The mass of an object is a fundamental property of the object; a numerical measure of its inertia; a fundamental measure of the amount of matter in the object. The usual symbol for mass is 'm' and its SI unit is kilogram.

In science, the weight of an object is the force on the object due to gravity. Its magnitude (a scalar quantity), often denoted by W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g. Thus, W = mg. Since the weight is a force, its SI unit is Newton.

Simply stated, weight is the force acting vertically downward. The weight of an object is the force with which it is attracted towards the earth, that is:

F = m x g

An object's weight depends on its environment, while its mass does not. The SI unit of weight is the same as that of force, that is, Newton (N).The force acting on an object perpendicular to the surface is called thrust. The effect of thrust depends on the area on which it acts. Thus:

Thrust = F = m x g

The thrust on unit area is called pressure. SI unit of pressure is N/m² or Nm^-2 or pascal, denoted by Pa.

#Materials required: 

solid iron cuboid, scale and dry sand filled tub.

#The Procedure: 

Fill ¾ ths of a tray with dry sand and level it.

·                     Measure the dimensions of a solid iron cuboid accurately using a scale. Mark the three faces of the cuboid as A, B and C.

·                     Place the solid iron cuboid by the surface A on the plane levelled sand in the tray.

·                     After a few minutes, remove the Iron cuboid and you will see that it has made a depression in the sand. 

·                     Measure the depth (depression) it has made in the sand using the scale. 

·                     Repeat the same procedure for the other two surfaces.  

#Observations: 

Gravitational force on the environment = …….. .  m/s²

1.     Calculate the area occupied by each surface of the solid iron cuboid. 

·                     Area occupied by surface A in the sand = .............cm²

·                     Area occupied by surface B in the sand = ............. cm²

·                     Area occupied by surface C in the sand = ............. cm²

2.     Calculate the pressure made by each surface of the solid iron cuboid. 

·         Pressure made by the surface A in the sand = ............. N

·         Pressure made by the surface B in the sand = ............. N

·         Pressure made by the surface C in the sand = ............. N

3.     Calculate the Depression.

·         Depression made by the surface A in the sand = ............. cm

·         Depression made by the surface B in the sand = ............. cm

·         Depression made by the surface C in the sand = ............. cm

#Learning outcomes

1.     The depression in sand is greater when the solid iron cuboid is placed on its least surface area.

2.     The pressure exerted by the smallest surface area is greater than the other surfaces with larger areas.

3.     Thus, the students understood the theories of force, area pressure, depression and their dependence on each other. 

#Precautions:

1.     Dried sand must be used.

2.     The tray must have significant length and width.

3. Appropriate cuboid of dimension must be used.