Lab report : Center of gravity
Aim:
- Understanding and learning the techniques of determining centre of gravity.
- Locate of centre of gravity of different uniform lamina.
Introduction to Lab session:
A common thought has risen to investigate around watching an apple fall to the ground. Newton made massive imaginary toward the motion of the apple, thus developing the concept of gravity. There are four primary forces acting in the world which are gravitational, the electromagnetic, the weak, and the strong. Gravity force might be the most recognized force in our basic life. All objects on the surface have center of gravity which maintain the object on the surface. Basically center of gravity is defined as a geometric property of any body and it is located in the average of the weight of an object. The motion of any object act on a surface can perfectly describe in the terms of transformation of the center of gravity of the object and the rotation of the object about its center of gravity, and therefore has a huge impact in our daily life. An application of this when the ball is thrown it is rotated around it is center of gravity. In the other words, anybody move through space while rotating constantly rotates around it center of gravity. Center of gravity is varying between small and large objects. In the other meaning, greater mass will requires greater force of gravity and vice-versa for small mass. `
Apparatus:
- Engineer's Metric ruler
- Cross sections of plastic lamina
- Papers (A4)
- Weight
- Pencil
- Scissors
Safety Issues:
- Keep the weight far away from the edge of the table, otherwise it might drop on the floor
- Be aware when you cut the papers using the scissors it could harm your hand
Methodology:
- Use A4 papers to cover the lamina and fixed at the edges using scissor and sellotape.
- Make holes at the corners of a lamina then attach the lamina to the pivot mounted on the wall in order to swing freely with the paper side facing outwards.
- In this step, the centre of gravity of lamina can be indicated from the point where the two lines intersected with reference to fixed axes on the other hand outcomes of x and y will unlike based on the location of axes
- Discuss and find out sources of errors among experimental and theoretical outcomes
Theory:
The point on a body which its weight can be considered to be concentrated is defined as center of gravity. This point might varying in regular and irregular bodies and also can be placed inside or outside the object. For example, in the regular bodies it is situated at the geometric center of the body. However, in the irregular bodies it can be determined by balancing method. Basically, balancing method based on drawing plum lines from several points of suspension and intersection of these plums represent the center of gravity of the body.
Results:
Theoretical outcomes:
(1) (2)
Aa=High × width = 5 × 126= 63 m2 , Bb=High × width = 5 × 17= 85m2
Ax Radius = 2.5cm Bx Radius = 8.5 + 5 = 13.5 cm
Ay Radius = 6.3 cm By Radius = 3.7 + 2.5 = 6.2 cm
(3)
Cc=High × width =12.5 × 3 = 37.5 m2
Cx Radius = 1.5 + 17 + 5 = 23.5 cm
Cy Radius = 6.25 cm
x = 63 ×2.5+85×13.5+(37.5×23.5)(63+85+37.5) = 2186.25185.5 = 11.7886 cm
y = 63×6.3+85×6.2+(37.5×6.25)(63+85+37.5) = 1158.275185.5 = 6.244 cm
Experimental outcomes:
x = 11.6 cm , y = 6.4cm
The percentage of errors:
For x = theoretical result-experimental resultTheoretical result = (11.786-11.6)11.786 × 100
= 1.578 %
For y = (6.244-6.4)6.244 × 100 = 2.498 %
Discussion:
This is lab meant to determine the center of gravity on a lamina. Center of gravity refers to the point in the body where the resultant torque caused by gravitational force is zero. This point of the body may be used to summarize the gravitational interactions acting on a body. When considering uniform gravitational field, the center of mass be the same as the center of gravity (Douglas, 2011).
When it comes to non-uniform field, it is essential to consider other gravitation effects such as torque, potential energy and force. In non-uniform objects such as the lamina, it is not possible to use the center of mass for calculation. For this reason, it becomes necessary to use other methods to determine the center of gravity. The center of gravity depends on external fields and thus, its motion is difficult to determine compared to the motion of the center of mass. Center of gravity may be located in either inside or outside of the depending on shape of the object and whether the object is a regular or irregular. For irregular bodies such as the lamina, the center of gravity is determined by the use of balancing techniques. This is achieved by the use of different parts of suspension and then using intersecting lines to determine the center of gravity. It is easier to measure the center of gravity for irregular bodies because it is situated at the center of the body meaning that the center of gravity and the center of mass are the same (Eitel, & Yau, 2007).
Conclusion
Torque is the measure of the amount of force acing on abject that may make the object to rotate. The experiment for the determination of the center of gravity indicates that the there is a point in the irregular lamina that behaves in such a way as if all the body weight is acting on it. If the net torque on the lamina is zero, then it means that the lamina is in equilibrium. The comparison between the theoretical center of gravity and the one found through the experiment in determining the location of the center of gravity for the lamina indicate the center of gravity is different from the center of mass for irregular objects. In conclusion, the center of gravity refers to the point on the object where the weight may be applied in a manner that will sum the forces through the use of Newton second law.
Reference List
Douglas, I. (2011). Center of gravity. New York, Harper Voyager
Eitel, T., & Yau, J. (2007). Tim Eitel: center of gravity. New York, N.Y., PaceWildenstein
