- Frame of Reference: Changing a person’s frame of reference (group standards or norms) can change attitudes, especially when new group norms are introduced (Asch, Newcomb, Lewin).
- Group Decision is Powerful: Group discussion and collective decision-making are more effective in changing attitudes than lectures.
- Lewin’s Food Habit Study: The Discussion Method (32%) was more effective than the Lecture Method (3%) in changing food habits during WWII.
- Reason for Effectiveness: Active participation and ego involvement in discussion create stronger and more lasting attitude change.
- Industrial Study (Lewin & Butler, 1953): Supervisors showed more improvement in reducing bias through discussion compared to lecture and control groups.
- Indian Study (Kothurkar, 1953): Emotional appeal showed more attitude change than rational and discussion methods, though results were not strongly significant.
Definitions [12]
Definition: Aristotle's Fallacy
Aristotle's statement: “An external force is required to keep a body in uniform motion”.
Definition: Newton's First Law of Motion
"If no force is acting on a body, its velocity does not change, i.e., the body does not accelerate. In other words, if a body is stationary, it will remain stationary. If it is in motion, it will continue moving with the same velocity and in the same direction."
or
"An object continues to remain at rest or in a state of uniform motion along a straight line unless an external unbalanced force acts on it."
or
"Every inanimate object continues to be in its state of rest or of uniform unaccelerated motion unless and until it is acted upon by an external, unbalanced force."
Define Newton’s second law of motion.
Newton’s second law of motion states that the rate of change of momentum is directly proportional to force applied and takes place in the direction of the force.
Definition: Newton's Second Law of Motion
"The rate of change of momentum is proportional to the applied force, and the change of momentum occurs in the direction of the force."
Definition: Impulse of a Force
The quantity ‘change in momentum’ is separately named as the Impulse of the force.
Definition: Newton's Law of Motion
"Every action force has an equal and opposite reaction force which acts simultaneously."
The concise law statement is: "To every action (force), there is an equal and opposite reaction (force)."
Definition: Rolling Friction
"Friction between two bodies in contact when one body is rolling over the other, is called rolling friction."
Define centripetal force.
The force acting on a particle performing uniform circular motion along the radius and directed towards the centre of the circle is called the centripetal force.
The mathematical form of centripetal force is:
F = `mv^2/r`
where:
F = centripetal force,
m = mass of the object,
v = speed or velocity, and
r = radius
Definition: Kinetic Friction
Friction between two surfaces in contact when one body is actually sliding over the other body is called kinetic friction or dynamic friction.
or
The force of friction that comes into play when a body is in a steady state of motion over another surface is called the force of kinetic friction.
Definition: Static Friction
The frictional force that balances the applied force when the body is static (or at rest). It prevents sliding motion between two surfaces in contact.
Definition: Centripetal Force
Centripetal force is the force acting on a body moving in a circular path, in a direction towards the centre of the circular path.
OR
A force acts on any object moving along a circle and it is directed towards the centre of the circle. This is called the Centripetal force.
Define Centripetal force.
At each of circular path, the particle, instead of moving straight continuously, turn towards the centre. Therefore, the motion in the circular path is under the action of a force called the centripetal force.
Formulae [7]
Formula: Newton's First Law of Motion
\[\vec F\] = m \[\frac{d\vec{\mathrm{v}}}{dt}\] = m\[\vec a\] ... (for constant mass)
Thus, if \[\vec F\] = 0, \[\vec v\] is constant. Hence, if there is no force, velocity will not change. This is nothing but Newton's first law of motion.
Formula: Newton's Second Law of Motion
General Form: \[\vec F\] =\[\frac{d\vec{p}}{dt}\]
For Constant Mass: \[\vec F\] = m\[\vec a\]
Momentum: \[\vec p\] = m\[\vec v\]
Formula: Newton's Third Law of Motion
\[\vec{F}=\frac{d\vec{p}}{dt}=\frac{d\left(m\vec{\mathrm{v}}\right)}{dt}\]
Formula: Kinetic Friction
Fₖ = μₖ N
Where:
- Fₖ = Force of kinetic friction
- μₖ = Coefficient of kinetic friction (constant of proportionality)
- N = Normal reaction between the two surfaces in contact
Formula: Coefficient of Kinetic Friction
μₖ = Fₖ/N
The coefficient of kinetic friction is defined as the ratio of force of kinetic friction to the normal reaction between the two surfaces in contact.
Formula: Coefficient of Static Friction
μs = FL / N
Where:
- μs = Coefficient of static friction
- FL = Limiting force of friction
- N = Normal reaction
Formula: Static Friction
FL = μs N
Where:
- FL = Limiting force of friction (maximum static friction)
- μs = Coefficient of static friction (dimensionless constant)
- N = Normal reaction (normal force between surfaces)
Key Points
Key Points: Frame of Reference
Concepts [18]
- Intuitive Concept of Force
- Aristotle’s Fallacy
- The Law of Inertia
- Newton's First Law of Motion
- Newton’s Second Law of Motion
- Impulse of a Force
- Newton's Third Law of Motion
- Conservation of Momentum
- Equilibrium of a Particle
- Common Forces in Mechanics
- Friction
- Types of Friction>Rolling Friction
- Circular Motion and Its Characteristics
- Solving Problems in Mechanics
- Types of Friction>Kinetic Friction
- Types of Friction>Static Friction
- Frame of Reference
- Centripetal Force
