physics-class-11-unit-05-chapter-05-laws-of-motion-newtons-first-law-of-motion-lecture-5-8-g6cnuoo58bu

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Force </primary>
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- Force is a quantity which has a magnitude, and it also has a sense of direction.

- <span style="color:green"> Magnitude \& direction $\rightarrow$ Vector.</span>

- Vector follow parallelogram law of addition or the triangle law of addition.

- <span style="color:green">Force $\rightarrow$ Vector.</span>

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<footer style = "font-size: 18px">Concept of Force $\rightarrow$ Force $\rightarrow$ <span style = "color:blue"> Force </span> $\rightarrow$ Force $\rightarrow$ Force </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Contact Forces </primary>
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- Body in contact with a second body.

- Contact between A and B can give rise to a force.

- Examples of such: contact forces.

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<footer style = "font-size: 18px">Force $\rightarrow$ Force $\rightarrow$ <span style = "color:blue"> Contact Forces </span> $\rightarrow$ Reaction Forces $\rightarrow$ Non- Contact Force </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Reaction Forces </primary>
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- Friction force : A force which tends to prevent the relative motion between the two surfaces.

- Force between two solid bodies in contact is called as the friction force.

- Air is in contact with the aeroplane and air will put a viscous force on the aeroplane.

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<footer style = "font-size: 18px">Force $\rightarrow$ Contact Forces $\rightarrow$ <span style = "color:blue"> Reaction Forces </span> $\rightarrow$ Non- Contact Force $\rightarrow$ Electrostatic </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Non- Contact Force </primary>
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- Some other forces which do not require any contact between the 2 bodies.

- Example:- <span style="color:blue">Force due to gravity $\rightarrow \propto \frac{1}{r^2}$</span>

- r $\rightarrow$ <span style="color:green"> Seperation between the two bodies.</span>

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<footer style = "font-size: 18px">Contact Forces $\rightarrow$ Reaction Forces $\rightarrow$ <span style = "color:blue"> Non- Contact Force </span> $\rightarrow$ Electrostatic $\rightarrow$ Qualitative Effect of Force </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Motion of a Ball </primary>
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- The ball is assumed to be a particle.

- Example: let us say there is a rod of length L.

- Study the motion of the rod.

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<footer style = "font-size: 18px">Qualitative Effect of Force $\rightarrow$ Particle $\rightarrow$ <span style = "color:blue"> Motion of a Ball </span> $\rightarrow$ Rigid Body $\rightarrow$ Rigid Body </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Momentum </primary>
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- Momentum $\vec{p}$ is defined as the product of mass and velocity.

- <span style="color:green"> $\vec{p} \equiv m \vec{v}$</span>

- Where:

- <span style="color:blue"> m $\rightarrow$ Scalar quantity.</span>

- <span style="color:green"> $\vec{v} \rightarrow$ Vector quantity.</span>

- <span style="color:green"> $\vec{p} \rightarrow$ Vector quantity.</span>

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<footer style = "font-size: 18px">Rigid Body $\rightarrow$ Rigid Body $\rightarrow$ <span style = "color:blue"> Momentum </span> $\rightarrow$ First Law of Motion $\rightarrow$ Uniform Motion </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Galileo Law </primary>
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- Because of the gravity the acceleration of ball as it moves down this is <span style="color:green">positive</span>.

- When ball moves up the incline, then the acceleration is <span style="color:green">negative</span>.

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<footer style = "font-size: 18px">Uniform Motion $\rightarrow$ Galileo Law $\rightarrow$ <span style = "color:blue"> Galileo Law </span> $\rightarrow$ Balls Rolls Down the Incline $\rightarrow$ Galileo Law </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Balls Rolls Down the Incline </primary>
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- $ \theta=\alpha, d_1 \approx d_2 . $

- $ \alpha>\theta,  d_2<d_1 $

- $ \alpha<\theta, d_2 > d_1, $

- $\alpha =0 \rightarrow d_2 \rightarrow \infty$

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<footer style = "font-size: 18px">Galileo Law $\rightarrow$ Galileo Law $\rightarrow$ <span style = "color:blue"> Balls Rolls Down the Incline </span> $\rightarrow$ Galileo Law $\rightarrow$ Newton's First Law of Motion </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Galileo Law </primary>
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- <span style="color:green">**Galileo**</span> $\rightarrow$ Body is at a state of rest or in uniform motin then both these states  are equivalent and no force is required to maintain these states.

- Property of the body to maintain its state of rest or uniform motion: Inertia.

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<footer style = "font-size: 18px">Galileo Law $\rightarrow$ Balls Rolls Down the Incline $\rightarrow$ <span style = "color:blue"> Galileo Law </span> $\rightarrow$ Newton's First Law of Motion $\rightarrow$ Newton's First Law of Motion </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Newton's First Law of Motion </primary>
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- Body does not change its state of rest or uniform motion unless an external force is applied on it

- Each body continues to be in a state of rest or uniform motion unless  compelled by an external force to act otherwise

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<footer style = "font-size: 18px">Balls Rolls Down the Incline $\rightarrow$ Galileo Law $\rightarrow$ <span style = "color:blue"> Newton's First Law of Motion </span> $\rightarrow$ Newton's First Law of Motion $\rightarrow$ Two Types of Situations </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Newton's First Law of Motion </primary>
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- Rest, Uniform motion

- Common kinematic quantity

- <span style="color:green"> $\vec{a}=0$</span>

- If the net external force on a body =<span style="color:green">0</span>, then its acceleration = <span style ="color:green">0</span>.

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<footer style = "font-size: 18px">Galileo Law $\rightarrow$ Newton's First Law of Motion $\rightarrow$ <span style = "color:blue"> Newton's First Law of Motion </span> $\rightarrow$ Two Types of Situations $\rightarrow$ Two Types of Situations </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Two Types of Situations </primary>
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- <span style="color:green">**b) More often,**</span>

- We know if acceleration of a body, we may not know all the force acting on the body.

- If <span style="color:blue">$\vec{a}=0$</span>, then sum of external forces acting on a body = 0.

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<footer style = "font-size: 18px">Newton's First Law of Motion $\rightarrow$ Two Types of Situations $\rightarrow$ <span style = "color:blue"> Two Types of Situations </span> $\rightarrow$ Example $\rightarrow$ Inertia </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Example </primary>
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- Force due to <span style="color:green">Gravity</span> = <span style="color:green">Weight</span> = <span style="color:green">mg</span>

- Acceleration of the sphere, <span style="color:green">$\vec{a_{sphere}} = 0$</span>

- $\implies$ Sum of forces on the sphere must be 0.

- Reaction force <span style="color:blue">R = mg</span>

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<footer style = "font-size: 18px">Two Types of Situations $\rightarrow$ Two Types of Situations $\rightarrow$ <span style = "color:blue"> Example </span> $\rightarrow$ Inertia $\rightarrow$ Inertia </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Inertia </primary>
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- Suppose we are moving in a bus and initially the bus is at rest and as the driver starts the bus, acceleration body tends to fall back.

- <span style="color:green">**Reverse observation:**</span> bus or a car and there is a braking effect. The brakes are applied on the car and we find the body of the passenger tends to fall in front.

* Feet are in touch with the floor of bus/car

* And as the car accelerates, feet constantly touch the floor. Because of friction, no relative motion between feet & bus/car. Feet have the same acceleration

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<footer style = "font-size: 18px">Two Types of Situations $\rightarrow$ Example $\rightarrow$ <span style = "color:blue"> Inertia </span> $\rightarrow$ Inertia $\rightarrow$ Uniform Motion </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Inertia </primary>
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- <span style="color:green">**Body**</span>, $\rightarrow$ Not one rigid body.

- Top parts of the body, when the bus starts $\rightarrow$ Tends to maintain it state of rest.

- <span style="color:blue">Feet $\rightarrow$ ahead</span>

- Body tends to fall backward.

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<footer style = "font-size: 18px">Example $\rightarrow$ Inertia $\rightarrow$ <span style = "color:blue"> Inertia </span> $\rightarrow$ Uniform Motion $\rightarrow$ Galilean Invariant Frames </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Uniform Motion </primary>
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- State of rest and state of uniform motion

- Equivalent as far as effect of force is concerned.

- Such frame of reference which are either at rest or move with respect to each other at constant velocities.
- <span style="color:green">(uniform motion)</span>

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<footer style = "font-size: 18px">Inertia $\rightarrow$ Inertia $\rightarrow$ <span style = "color:blue"> Uniform Motion </span> $\rightarrow$ Galilean Invariant Frames $\rightarrow$ Thank You </footer>

### <Success style="font-size:25px"> Laws Of Motion Newtons First Law Of Motion L-5 </Success>
### <primary style="font-size:24px"> Galilean Invariant Frames </primary>
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- State of rest or state of uniform motion will be determined with respect to a frame of reference.

- So such frames of reference which are either at rest or if they move with respect to each other at constant velocities, which means uniform motion, such frames are equivalent.

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<footer style = "font-size: 18px">Inertia $\rightarrow$ Uniform Motion $\rightarrow$ <span style = "color:blue"> Galilean Invariant Frames </span> $\rightarrow$ Thank You $\rightarrow$  </footer>