newton's second law

April 16, 2013

[DYNAMIC:NEWTON’S SECOND LAW]

Experiment 2 DYNAMIC – NEWTON’S SECOND LAW

NUR SYUHAIDAH BT ZAIDI CPM97/12C GROUP D 16th APRIL 2013 MR.ZIKRI

GROUP’S MEMBER: - WAN NUR'ATIQAH HANIS BT WAN SOLAH - FATHIAH HANIM BT SHAKIRIN - AZWINA BT JUAZER RIZAL - FARAH ADIBAH BT MOHD JOHARI -SITI THAHIRAH BT ABUL KALAM


April 16, 2013

Objective :

a) To determine the relationship between velocity and time b) To determine the acceleration of the motion of the trolley c) To find the constant force exerted on the trolley

Introduction: Newton's second law of motion pertains to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object. The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object. As the force acting upon an object is increased, the acceleration of the object is increased. As the mass of an object is increased, the acceleration of the object is decreased. Force is equal to mass times acceleration (for constant mass). So ,An object will accelerate in the direction of any net force applied to it. The greater the force, the greater the acceleration. The greater the mass, the slower the acceleration. This means that the rate an object is slowing down or speeding up (acceleration) depends on how hard it is hit, pushed, or pulled (force) and the mass of the object.

This means that the rate an object is slowing down or speeding up (acceleration) depends on how hard it is hit, pushed, or pulled (force) and the mass of the object. Let’s take a look at some examples to learn more about Newton’s Second Law. A truck hits a car; the car moves forward. The truck provides the force, the car is the mass, and the acceleration is how quickly the car (mass) moves forward. The larger and heavier the car (mass) is, the more force it takes to move it. If the car is very light, it will move forward quicker than if the car is very heavy. If you throw a 10-lb. weight and a 2-lb. weight with the same amount of force, the 2 lb. weight will travel faster than the 10-lb. weight. That is because there is less mass to be moved. Although few people could quote Newton’s Second


April 16, 2013

Law, everyone has used it before. It is part of everyday life; the heavier something is, the harder you have to push to move it. You don’t really spend a lot of time thinking about it because your brain knows it so well. For example, if you think a door is heavy, your brain will automatically tell you to apply a lot of force, but if the door is actually light you will end up slamming it.

Theory :

The equation of Newton’s motion for any mass m that move in the velocity respect to time will give force F onto it that given by

F = ma

where a =

or

is an acceleration

F=m

Acceleration a can be derived from the slope of the v – t graph as shown in the Figure 1 :


April 16, 2013 v

t

Figure 1

Apparatus :

i) ii) iii) iv)

Trolley without friction ‘Runway’ plane ‘Timer’ meter ruler

Figure 2

Procedure:

=a

April 16, 2013

a) b) c) d) e) f) g) h) i) j)


Set up the apparatus as in the Figure 2. Measure and record the mass of the trolley. Start the experiment on top of the on runway. Release the trolley. Start the timer simultaneously. Stop the timer when the car reaches the bottom of the track. Repeat steps c) – e) for 4 different lengths with 5cm decrements of each. Repeat the experiment by adding 0.05 kg load on the trolley. Draw the table as in table 1 below for the two masses of the trolley. Plot graph v vs .̅ Calculate the slope of the graph

RESULTS: Velocity of each Interval V1 V2 V3 V4 V5 V6 V7 V8 V9 V10

Without Load

1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05 2.10 2.15

With load(50g) (m/s) 0.63 0.65 0.70 0.75 0.80 0.80 0.85 0.90 0.90 0.95

Time(s)

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10


April 16, 2013

VELOCITY(M/S) AGAINST TIME(S) (WITHOUT LOAD) 2.5

Velocity(m/s)

2

1.5

y = 5x + 1.65

1

0.5

0 0

0.02

0.04

0.06

0.08

0.1

0.12

Time taken (s)

VELOCITY(M/S) AGAINST TIME(S) (WITH LOAD)

1.2

Velocity(m/s)

1 0.8 y = 3.5939x + 0.5953

0.6 0.4 0.2 0 0

0.02

0.04

0.06 Time taken (s)

0.08

0.1

0.12


April 16, 2013

Discussion: In this experiment, we need to find the velocity of the trolley at two different conditions; without load and with load by using the timer(tickertape). After the experiment is done ,the values of the velocity are calculated by measuring the length of two distance point on the ticker tape . The total time is considered as 0.1 so if ten values of distance are taken , time taken is 0.02 each . Each period between dots is a 'tick' of time.We calculated the values of velocity of each interval by using this formula:

Velocity:

V= =1.70 ms-2

In each experiments ; we calculated the velocity using the formula above. Velocity is a measure of the speed of an object that is moving in a specific direction. Velocity of the trolley without load is faster than the velocity of the trolley with load. The velocity of the trolley is affected by the mass of the trolley . So, if we increased the mass of the trolley, the acceleration is decreased . According to the result of the experiment, the velocity of trolley with load is slower as predicted . As we refer to Newton’s second law, if the mass is increased , acceleration of the object is decreased(constant force). The acceleration is inversely proportional to the mass. So, in order to increase the acceleration , we must decrease the mass of an object. The uncertainty of the values in the experiment may due to the some errors along the experiment. Random errors are unpredictable. They are chance variations in the measurements over which you as experimenter have little or no control. There is just as great a chance that the measurement is too big as that it is too

April 16, 2013


small. Since the errors are equally likely to be high as low, averaging a sufficiently large number of results will, in principle, reduce their effect. So, the experiment must be repeated twice to get an accurate result. In order to avoid the parallax errors , we must make sure the position of the eyes must be perpendicular to the ruler when measuring the distance. Other than that, systematic error are errors caused by the way in which the experiment was conducted. In other words, they are caused by the design of the system. Systematic errors cannot be eliminated by averaging . In principle, they can always be eliminated by changing the way in which the experiment was done. In actual fact though, you may not even know that the error exists. So, we must avoid from adding external forces during releasing the trolley since it will affect the measurement.

Conclusion: The experiment conducted is succeed . According to the both of the graphs, the acceleration of the trolley without load is faster than with load. The acceleration of the trolley without load is 5 ms-2 while trolley with load is 3.6 ms-2.It have approached the principle of the newton’s second law( a=m/f). The acceleration is inversely proportional to the mass. Thus, the greater the mass, the less the acceleration.

References: http://www.scribd.com/doc/94383213/Physics-Lab-Report Physics reference book ;pearson;James S.Walker http://www.digipac.ca/chemical/sigfigs/experimental_errors.htm

newton's second law

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