Laboratorial Report 4

Transcription

1 Title: Acceleration Laboratorial Report 4 Created to fulfill the assignment for Mechanic and heat EN222 subject By: 1. Debby Syefira ( ) 2. Damavara ( ) 3. I Wayan Surya Aryana ( ) Lecturers: Lina J Diguna Fatih Sampoerna University Performed: Jakarta, June 12 th, 2015

2 Abstract Acceleration is basically explained as a changing of an object velocity that happen over the period of time needed by that object to alter the velocity. This meaning is theoretically applied to all object that possess a velocity (whether the velocity is zero or not). Since the acceleration is holding an important role in the physics phenomenon (in which one of the phenomenon is falling object), this principle of acceleration is consequently leading the student to perform the fourth experiment. This experiment is basically dealing with the concept of acceleration, velocity, and time. By experiencing three difference declivity distance, the experiment is underwent by recording the time needed for the object to reach a certain point in a certain distance. As the experiment done, the student is expected to be able to explained the relationship between velocity, time and acceleration; this relationship include the increasing value of velocity as the object traveled down the ramp, the constant value of acceleration as the object traveled down, and the phenomenon of the passengers in the car during a sudden stop. Keyword: Acceleration, Velocity, and Time

3 CHAPTER I OBJECTIVES The objective of this experiment is: To calculate the acceleration of an object rolling down and inclined plane.

4 CHAPTER II METHODOLOGY 2.1 Materials The materials that are being used in the experiment are listed in the table below: Table 1. Material Used in the Experiment Materials from Label or box/bag Quantity Item description Student provide 1 Ramp about 1-2 meters long made of wood, grooved tromp or molding, or stiff cardboard 1 Stopwatch digital 1 Tape measure, 3 m 1 Drinking straw From LabPag 1 Protractor, plastic 1 String and weight bag Marble, bolt, & spring bag 1 Marble 2.2 Procedures 1. Set up a ramp as shown in Figure 1. Depending on the length of the board mark off three distances along the ramp, such as 30 cm, 60 cm and 90 cm or 50 cm, 100 cm, and 150 cm. The wider the spacing on a longer board may give slightly better data. Prepare data and calculation sheets similar to the one that follows. 2. Measure the height of the ramp and record. 3. Measure the angle of the inclined ramp using a protractor. You may use the protractor with plumb line you used in the previous trigonometry experiment (see Figure 2).

5 150 cm 100 cm 50 cm Figure 2. Inclined Ramp 4. Hold the marble at the top of the ramp. 5. Release the marble and start the stopwatch simultaneously. 6. As the marble passes the first marked distance, stop the watch. 7. Record the time to the nearest tenth second in Table 2 below: Table 2. Data Record Figure 1. Protractor with Plumb Line Height of ramp: m Distance (x) TRIAL No. m Time (t) - seconds Angle of incline = o Velocity (v) m/s Average = Average = Average = Average = Average = Average = Average = Average = Average = Acceleration (a) m/s 2 8. Repeat the procedure at least four times. 9. Repeat timing to the second marked distance, third distance, etc.

6 CHAPTER III RESULT AND DISCUSSION 3.1 Theory Speed and Acceleration Before Galileo, the object that fall in certain height would fall in certain speed depend on the Earth element contain, its weight. The idea made Galileo challenge himself when he was the junior professor at the University of Pisa. He suggested that all objects, regardless of size or mass, would fall at the same rate if the effect of air resistance were removed. He also maintained that the speed of the falling object is not constant, as he had been assumed, but continues to increase constantly as long as the object falling. Because of Galileo, now people know that the rate of change (acceleration) is constant, not the velocity. Galileo showed that, with constant acceleration, a ball rolling down an inclined plane will travel a distance proportional to the square of the elapsed time (x = ½ at 2 ). Newton s first law, states that a body at rest will remain at rest unless acted upon by an outside force, and a body in motion will continue in motion at the same speed and in the same direction unless acted upon by an outside force. Acceleration in material science, is the rate of progress of speed of an item. An object's increasing speed is the net aftereffect of any powers following up on the article, as portrayed by Newton's Second Law. The SI unit for quickening is the meter every second squared (m/s2). Increasing speeds are vector amounts (they have extent and course) and add as indicated by the parallelogram law. As a vector, the figured net power is equivalent to the result of the object's mass (a scalar amount) and the quickening. (Wikipedia, 2015) Velocity is a vector quantity that refers to "the rate at which an object changes its position." Imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. Another way to accelerate the object is to change the direction of movement. This means that a car going around a corner is undergoing acceleration because its velocity in terms of direction is changing even if the car s speed, as seen on the speedometer, is constant. (Classroom, 2015)

7 As discussed above, an object falling under the influence of gravity accelerates. From the studies, people can recall the four kinematic equations for uniformly accelerated motion of an object starting from the rest, where v = velocity, a = acceleration, and x = distance. Equation 1: v = at Equation 2: x = ( v 2 ) t Equation 3: v 2 = 2ax Equation 4: x = 1/2at² 3.2 Result Table 3. Result of the Experiment Height of Ramp = m Angle of Incline = 2 TRIAL No. Distance (x) m Time (t) s Velocity (v) m/s Acceleration (a) m/s² Average = Average = Average = Average = Average = Average = Average = Average = Average = 0.318

8 3.3 Discussion The table above is basically showing the data finding that is needed to calculate the velocity and acceleration. In the experiment we took each of the distance five times to eliminate the error. After knowing the time we can calculate the velocity using equation 2: x = ( v 2 ) t v = 2x t Sample calculation of velocity using trial data no.1: V = 2 (0.3)/ V = 0.6/1.184 V = m/s As the distance of the x is increasing, the value of the velocity also increase. The value of the time is indirect proportional to the velocity so if the time shorter it will make the velocity has bigger value of velocity. After knowing the velocity, we calculate the acceleration using equation 1: v = at a = v t Sample Calculation of acceleration using trial no.1: a = 0.507/1.184 a = m/s 2

9 3.4 Answering Questions 1. Newton s first law says a body at rest will remain at rest unless acted upon by an outside force, and a body in motion will continue in motion at the same speed and in the same direction unless acted upon by an outside force. What forces were acting on the marble as it traveled down the ramp? Answer: If a body experiences an acceleration (or deceleration) or a change in direction of motion, it must have an outside force acting on it. Outside forces are sometimes called net forces or unbalanced forces. Net force is the overall force acting on an object. In order to calculate the net force, the body is isolated and interactions with the environment or other constraints are represented as forces and torques in a free-body diagram. The net force in this movement consist of two force which are friction force and parallel force that react in the same time. The property that a body has that resists motion if at rest, or resists speeding or slowing up, if in motion, is called inertia. Inertia is proportional to a body's mass, or the amount of matter that a body has. The more mass a body has, the more inertia it has. (Wikipedia, Net Force, 2015) The net force does not have the same impact on the development of the article as the first framework strengths, unless the purpose of utilization of the net power and a related torque are resolved so they shape the resultant power and torque. It is constantly conceivable to focus the torque connected with a state of use of a net constrain so it keeps up the development of the item under the first arrangement of strengths. (Wikipedia, Net Force, 2015) With its related torque, the net power turns into the resultant constrain and has the same impact on the rotational movement of the article as every single genuine power taken together. It is feasible for an arrangement of strengths to characterize a without torque resultant power. For this situation, the net power when connected at the best possible line of activity has the same impact on the body as the greater part of the strengths at their purposes of utilization. It is not generally conceivable to discover a without torque resultant power. (Wikipedia, Net Force, 2015)

10 2. Did the velocity of the marble increase as it traveled down the ramp? Answer: Yes, the velocity of the marble is increasing since its marble goes down the ramp it accelerates do to gravity or earth s pull on the marble. The velocity of the ball would increase at it goes down the ramp due to the acceleration of gravity. Neglecting friction, at the bottom of the ramp, the velocity of the ball would stay the same. The marble starts out with 0 velocity and as it goes down the velocity is increasing. 3. Did the acceleration of the marble increase as it traveled down the ramp? Answer: The acceleration will stay constant. External changes need to be done to change the marble's acceleration. The net power causes the increasing speed. Force parallel = m * g * sin θ Friction force = µ * m * g * cos θ Net force = m * g * sin θ µ * m * g * cos θ Acceleration = g * sin θ µ * g * cos θ = g * (sin θ µ * cos θ) The size of the quickening of the marble is reliant on the point of the incline and coefficient of rubbing. In the event that the point and coefficient of grinding stay steady. In this experiment, the angle (θ) is the same angle, there is no the changing. From the formula above, the acceleration is affected by the angle, if the angle change, the acceleration will change, but if the angle does not change, the acceleration is steady. 4. What would happen to the velocity and acceleration of the marble if the ramp were steeper? How about if the ramp were vertical? If you have trouble answering this, repeat the experiment with a steeper ramp. Answer: If the ramp is stepper, the chances is greater that the velocity and the acceleration would both be greater. If the ramp were vertical it would definitely travel down at an accelerated speed since it would be going straight down with nothing in its path to stop it.

11 5. As you ride in a car, your body is at rest relative to the car but in motion relative to the street. What might happen to the passengers in a car during a sudden stop or crash if there are loose objects stowed by the rear window of the car? Answer: When the car is in steady velocity, the passengers will not notice the movement of the car. When the car suddenly stop, or crashed something out side of the car, the velocity will change and you will notice the change of the velocity. In this stage, we can see that you react with acceleration as accelerometers but not react with velocity.

12 CHAPTER IV CONCLUSION 4.1 Conclusion 1. The forces that act on the marble as it traveled down the ramp would be determined by using a free body diagram. 2. The velocity of the ball would increase at it goes down the ramp due to the acceleration of gravity. 3. External changes need to be done to change the marble's acceleration. 4. The steeper the ramp, the greater the velocity and acceleration. 5. During a sudden stop or crash of a car, the passenger will react with acceleration as accelerometers but not react with velocity. 4.2 Recommendation 1. There should be many times of experiment s trial for each distances chosen, in order to get a smaller error on the result. 2. The distance of the marked distance along the ramp should be increased. 30cm and 50cm is too short. A too short distance like those will make the observer harder to observe a very short time traveled given.

13 REFERENCES Classroom, T. P. (2015, June 15). Speed and Velocity. Retrieved from The Physics Classroom: Wikipedia. (2015, June 14). Acceleration. Retrieved from Wikipedia The Free Encyclopedia: Wikipedia. (2015, June 16). Net Force. Retrieved from Wikipedia The Free Encyclopedia: