Name: 1.LAWS OF MOTION
Uploaded: 2022-02-27
Duration: 7 min 6 s
Description: 1.LAWS OF MOTION. Ø Motion Ø Distance and displacement Ø Acceleration Ø Newton’s laws of motion and related equations ..

1.LAWS OF MOTION. Ø Motion Ø Distance and displacement Ø Acceleration Ø Newton’s laws of motion and related equations .. 

Scene 1

Ø  Motion  Ø Distance and displacement Ø  Acceleration  Ø Newton’s laws of motion and related equations .

Motion of an object. 1.The flight of a bird 2 . A stationary train 3. Leaves flying through air 4. A stone lying on a hill. 

Scene 2

1.The  flight of a bird  2 . A stationary  train 3. Leaves flying through  air   4. A stone lying on a hill

Think about it.. 1. You are travelling in a bus. Is the person sitting next to you in motion? 2 . What do you take into consideration to decide if an object is moving or not?. 

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1. You are travelling in a bus. Is the person sitting next to you in motion? 2 . What do you take into consideration to decide if an object is moving or not?

M otion is a relative concept.. If the position of an object is changing with respect to its surroundings, then it is said to be in motion. Otherwise, it is said to be at rest.. 

Scene 4

If the position of an object  is changing  with respect to its  surroundings, then  it is said to be in motion. Otherwise, it  is said  to be at rest.

Displacement and distance. B (a) Sheetal and Prashant 's house (b) 500 m Path A School 1200 Path B Sangeeta's house. 

Scene 5

B
(a)
Sheetal and
Prashant 's house
(b)
500 m
Path A
School
1200
Path B
Sangeeta's house

1. Measure  the distance between  points A  and B in different  ways as  shown  in figure (a) 2. Now measure the  distance along the dotted  line.  Which distance  is  correct according  to you and why?

Scene 6

A.  Sheetal  first went to her  friend  Sangeeta’s   house on her way to  school (see figure b ). B.  Prashant  went straight from home to school. Both are walking with the same  speed. Who  will take less time to  reach the  school and  why? In  the  above example , is there a difference  between the  actual distance and  the distance  travelled? What is it?

‘Distance’ is the length of the actual path travelled by an object in motion while going from one point to another. 

Scene 7

‘Distance’ is the length of the actual path travelled by an object in motion while going from one point to another

Displacement  is the minimum distance  between the  starting and finishing points

Even if the displacement of an object is zero, the actual distance traversed by it may not be zero.. 

Scene 8

1. Every morning,  Swaralee  walks round the edge of a circular field having a radius of 100 m. As shown in figure 1.2 (a), if she starts from the point A and takes one round, how much distance has she walked and what is her displacement?

2. If a car, starting from point P, goes to point Q (see figure 1.2 b) and then returns to point P, how much distance has it travelled and what is its displacement?

Even if the displacement of an object is zero, the actual distance traversed by  it may not  be zero.

Can you recall?. 1. What are vectors and scalars? 2 . Which of the quantities distance, speed, velocity, time and displacement are scalars and which are vectors?. 

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1. What are vectors and scalars? 2 . Which of the quantities distance, speed, velocity, time  and displacement  are scalars and which are vectors?

Scene 10

Equations of motion using graphical method. v = u + at This is the relation between velocity and time . s = ut +1/2 at2 This is the relation between displacement and time. v2 = u2 + 2as This is the relation between displacement and velocity .. 

Scene 11

Equations of motion using graphical method

v = u + at  This is the relation between velocity and time . s =  ut   +1/2  at2  This is the relation between displacement and time. v2  = u2 + 2as  This is the relation between displacement and velocity .

Newton studied motion of an object and gave a set of three equations of motion. These relate the displacement, velocity, acceleration and time of an object moving  along a  straight line.

Suppose an object is in motion along a straight line with initial velocity ‘u’. It  attains a  final velocity ‘v’ in time ‘t’ due to acceleration ‘a’ its  desplacement  is ‘s’. The  three equations  of motion can be written as

Equation describing the relation between velocity and time. 

Scene 12

Equation describing the relation between velocity and time

Figure 1.9 shows the change in velocity with time of a uniformly accelerated object. The object starts from the point D in the graph with velocity u. Its velocity keeps  increasing and  after time t, it reaches the point B on the graph.

( Final velocity – Initial velocity) =     Time

CD = at …… (i) (OC - OD = CD). Draw a line parallel to Y axis passing through B. This will cross the X axis in E. Draw a line parallel to X-axis passing through D. This will cross the line BE at A.. 

Scene 13

Draw a line parallel to Y axis passing through B. This will cross the X axis in E. Draw a line parallel to X-axis passing through D. This will cross the line BE at A.

v = u + at This is the first equation of motion.

Let us suppose that an object in uniform acceleration ‘a’ and it has covered the distance ‘s’ within time ‘t’. From the graph in figure 1.9, the distance covered by the object during time ‘t’ is given by the area of quadrangle DOEB.. 

Scene 14

Equation describing the relation between displacement and time

Let us suppose that an object in uniform acceleration ‘a’ and it has covered  the distance  ‘s’ within time ‘t’. From the graph in figure 1.9, the distance covered by the  object during  time ‘t’ is given by the area of quadrangle DOEB.

s = area of quadrangle DOEB    =  area (rectangle DOEA) + area of triangle (DAB)

But, AE = u, OE = t and (OE = DA = t) AB = at ( AB = CD )  from (i)

Newton’s second equation of motion is s =  ut   +1/2  at2

We have seen that from the graph in figure 1.9 we can determine the distance covered by the object in time t from the area of the quadrangle DOEB. DOEB is a trapezium. So we can use the formula for its area.. 

Scene 15

Equation describing the relation between displacement and velocity

We have seen that from the graph in figure 1.9 we can determine the distance covered by the object in time t from the area of the quadrangle DOEB. DOEB is a trapezium. So we can use the formula for its area.

s  = 1/2  × sum of lengths  of   ×    distance  between                  parallel sides              the  parallel sides

But,      a=   (v-u )                      t

(v-u)
——-——--—--—--——(iii)
a

s = area of trapezium DOEB. s = 1/2 × sum of lengths of × distance between parallel sides the parallel sides. 

1.LAWS OF MOTION

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