2.1 : Linear Motion :     Motion along a straight line.

1.  Distance The distance travelled by an object is the ______________ that is traveled by that object. Distance is a ________________. The SI unit of distance is ___________ .

2.  Displacement Displacement of an object from a point of reference, O is the _____________ of the object from point O in a _____________ direction. Displacement is a _____________ quantity. The SI unit of displacement is _______________.

Distance	Displacement
Total path length travelled from one location to another	The distance between two location measured along the ______________ path connecting them in specific location
Scalar quantity	Vector quantity
Has magnitude only	Has magnitude and direction
SI unit meter	SI unit meter

   Speed

1.      Speed is defined as the …………………… travelled in a certain interval of time or the …………………............ of distance traveled with time.

                                         Speed = Distance traveled

                                                             Time taken

2.      The speed of an object is a ……………………… quantity. The SI units for speed is …………………..

 Velocity

1.      Velocity is defined as the …………………….. travelled in a given  interval of time in a ………………………………….. or the rate of change of …………………….. traveled with time.

                                         Velocity = Displacement

                                                            Time take

2.      The velocity of an object is a …………………….. quantity. The SI units for speed is ………………..

Acceleration

1.      Acceleration is defined as the rate of change of velocity.

                                   Acceleration = Change of velocity

                                                               Time taken

                                                     a = v - u

                                                              t

                                                     v - the final velocity

                                                     u – the initial velocity

                                                     t – the time taken

1.      The ticker timer as shown  in figure is used in the laboratory to study motion.

2.      It can print dots on a tape at a steady rate.

3.      It is connected to an a.c . power supply of 50 Hz.

4.      The time taken to make 50 dots on the ticker tape is 1 s. Hence , the time interval between 2 consecutive dots ( 1 tick) is 1/50 = 0.02 s.

Calculation involved ticker tape :

What is the speed of the trolley ?

The ticker-tape charts constructed with 5-tick lengths is shown in the Figure  above. What is the velocity of the trolley if the ticker-timer was connected to a 50 Hz power supply?

quotes of the day

CHAPTER 2 : FORCE AND MOTION_ definition list

Linear Motion is the motion of an object in a straight line.

Kinematics is the study of the of motion objects without considering the forces that cause the motion of the object.

Distance is the total length of the path covered by a moving object.

Displacement is distance from one point to another in a particular direction.

Speed is rate of change of distance. Unit m s^-1

Velocity is the rate of change of displacement.

Average speed is total distance moved divided by total time taken.

Average velocity is total displacement divided by total time taken.

Acceleration is rate of change of velocity. Unit m s^-2

                                                                                                                       a = v - u

                                                                                                  t

Equations of linear motion with  uniform acceleration are as follows :

                                                      v = u + at

                                                     s = ut  + ½ at²

                                                   v²  =  u²  + 2 as       

Dynamics is the study of the motion and of the forces that cause the motion of that body.

Inertia is the resistance of an object to change of its motion. Inertia is non-physical quantity.

Mass of an object is the quantity of matter in that object.

Newton’s First Law of motion states, if no external force is acting on an object, it will, if stationary remain stationary, if moving keep moving at a steady speed in a straight line.

Momentum of an object is defined as a product of mass and its velocity. Unit kg m s^-1

 p = mv

Principle of conservation of momentum states that when two or more objects act on each other, their total momentum remains constant, provided there are no external forces acting on the system. 

(m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂)

Force acting on an object can cause changes to its size, shape, and state of rest, velocity, and direction of motion of the object.

 

Newton’s second law of motion states that force acting on an object is directly proportional to the rate of change momentum of the object in the same direction. F = ma

Impulse is the product of force and time for which the force acts during collision

Impulsive force is the force that acts on an object within a very short time such as during a collision.

F = mv – mu                                 t

Gravitational attractive force is the pull (force) of the earth on objects and it acts towards the centre of the earth

An object is in free fall when it falls under the influence of gravitational attractive force without the influence of other forces. (A free fall is situation whereby an object falls under the influence of gravitational attractive force only).

Gravitational acceleration is the acceleration of an object which falls freely.

Weight of an object is the gravitational force acting on it. Or

W = mg (m = mass, g = gravitational acceleration)

An object is in equilibrium if the resultant of forces acting on it is zero.

Newton’s Third Law of Motion states that for every force there is an opposite an equivalent  force against it.

A resultant force is a single force that represents in magnitude and direction two or more forces acting on an object.

Resolving a force is replacing a single force by a pair of perpendicular forces provided that the resultant of the two forces is equivalent to the single force.

Work done by constant force to move an object is equivalent to the product of the magnitude of its displacement and the components of the force, which is in the direction of the displacement.

W = F x s

Energy is defined as the capacity of a system to do work.

Gravitational Potential Energy is defined as energy obtained by an object due to its position.

                                                      E_p = W = Fs

                                                           = mg x h

                                                           = mgh

Elastic Potential Energy is defined as energy obtained by object due to its state (extension or compression)

                                                         E_p = ½ F x  

Kinetic Energy is defined as energy attained by an object due to its motion.

W = E_k = ½ m v²  

Conservation of Energy states that energy cannot be created nor destroyed but changes from one form to another.

Elasticity of a material is its ability to return to its original form and size when the force acting on it is removed.

Hooke’s law states that the extension of an elastic spring is directly proportional to the force acting on it provided that the limit of elasticity is not exceeded.

Spring constant is defined as force per unit extension of a spring.

A soft spring has a smaller k value whereas a stiff spring has a larger k value.

The work done when extending or compressing an elastic material is given by

The strength of a material is the ability of the material to withstand external forces before it breaks or snaps. Rattan is a strong but not rigid material. Concrete is both strong and rigid.

Rigidity is the ability of a material to withstand external forces acting on it without changing its size or shape. Glass is a rigid but not a strong material.

SIMPLE PENDULUM EXPERIMENT

1. Inference :  When the length of a simple pendulum increases, the period of oscillation also increases. // The period of pendulum is affected by the length of the thread.

2. Hypothesis :  The longer the length of a simple pendulum, the longer will be the period of oscillation

                           

      3.   Aim :  To find the relationship between the length of a simple pendulum and the period 

                       of oscillation.

      4.   Variable :  a) Manipulated variable : Length, l

               b) Responding variable  : Period, T.

               c)  Fixed variable            : Mass of pendulum bob. 

5.       Materials/ Apparatus : Retort stand, pendulum bob, thread, metre rule, stop watch.

 FUNCTIONAL DIAGRAM

7. Procedure     :

     a)  Set up the apparatus as shown in Figure above.// A small brass or

          bob was attached to the thread. The thread was held by a clamp of a

          the retort stand.

           

      b) The length of the thread , l  was measured by a metre rule, starting

           with 90.0 cm. The bob of the pendulum was displaced and released.

      c)  The time for 20 complete oscillations, t was taken using the stop

watch.  Calculate the period of oscillation by using, T = t / 20

      d) The experiment was repeated using different lengths such as

           80.0 cm. 70.0 cm, 60.0 cm, 50.0 cm and 40.0 cm.

Length of string, l / cm	Time taken for 10 oscillation, t (s)			Period of oscillation T	T2 (s2 )
	t 1	t 2	Average, t
40.0 50.0 60.0 70.0 80.0 90.0	25.2 28.1 31.0 33.5 35.7 38.2	25.1 28.2 31.0 33.6 35.9 37.9	25.2 28.2 31.0 33.6 35.8 38.1	1.26 1.41 1.55 1.68 1.79 1.91	1.59 1.99 2.40 2.82 3.20 3.65

8. Plotting the graph

Notes :

  a)   Plotting the graph

·         The graph should be labeled by a heading

·         All axes should be labeled  with quantities and their respective units.

·         The manipulated variable (l) should be plotted on the x-axis while the responding variable (T² ) should be plotted on the y-axis

·         Odd scales such as 1:3,  1:7 , 1:9 0r 1 :11 should be avoided in plotting  graph.

·         Make sure that the transference of data from the table to the graph is accurate.

·         Draw the best straight line.

- the line that passes through most of the points plotted such that is balanced by the number of points above and below the straight line.

·         make sure that the size  of the graph  is large enough,  which is, not less than half the size of the graph paper or.(  > 8 cm x 10 cm )

10. Discussion / Precaution of the experiment / to improve the accuracy

                 

a)      The bob of the pendulum was displaced with a small  angle

b)      The amplitude of the oscillation  of a simple pendulum  is small.

c)      The simple pendulum oscillate in a vertical plane only.

d)      Switch off the fan to reduce the air resistance

    11. Conclusion

                 The  length of simple pendulum is directly  proportional  to

      the square of the period  of oscillation. //

      T² is directly proportional to l  (the straight line graph passing

      through the origin)