Jeffery Shen's reflection on application of Newton's laws and equilibrium

We have been studying static equilibrium, pulley system, inclines and  torque for the past 2 months. In these two months, I practiced and learned how to apply the newton's laws and the principle of torque efficiently. By studying newton's laws and torque, I have now gained a better understanding of how physics can be applied into real life problems. In the following paragraphs, I am going to briefly introduce you to the wonderful world of newtons laws, how can it be applied and torque.

Newton's three laws are:

• Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it 
• F=ma, when an unbalanced force acts on an object it accelerates the object in the same direction ( of force)
• For every action there is an equal and opposite reaction( force occur in pairs). 

Although the laws seems very confusing at times, it is easy to understand if we think of the phenomenon that occurs around us.
For example, when we skate freely on a completely smooth ice, we will be traveling fast and far. However, if we wear our normal shoes and try to skate on a dry concrete floor, it is very unlikely for us to glide. This is because when on smooth ice, there isn't much of an external force to act against us, but on concrete floor, we would experience such force AKA friction.

The second law is the most powerful among the three, because it can actually enable us to perform calculations of dynamics. The formula F=ma is considered as the gold physics formula of high school.

The third law is also very easy to explain, imaging when you kick the wall really hard, the chance of you breaking your toes is pretty high. Force occurs in pairs.

Through understanding the newton's three laws, we can apply them to questions and real life problems.
In pulleys, when we consider the question as a whole system, it is mg+Mg=(m+M)a. Because neglect friction in pulleys, the only force acting is gravity.
If we need to calculate the tension in the rope, we need to split the system apart. However, the acceleration of the two masses and the tension in the ropes are the same.

The newton's laws can also applied to ramps. In ramps, because there is an incline, the object is not horizontal to the floor, so we must split the force of gravity into x and y components. Again, if we can identify forces acting on the object, it is easy to manipulate the laws and get the correct answer.

When a system is in static equilibrium, or translational equilibrium, it MUST have zero acceleration. Zero acceleration doesn't mean it has zero forces acting on it, it means the forces acting on the object are cancelled out. A good example is when we hang a picture on the wall, the rope or nail on the wall must provide enough amount of force to keep the picture from falling. The force exerts by the nail or tension in the rope cancelled out with the force of the gravity.

A nail or a rope must provide enough force to keep the picture from falling

When a system is in rotational equilibrium, all forces pass through a common point. Such force is called concurrent forces. torque=Force*distance of the from the pivot point. A good example of rotational equilibrium is a balanced balance. A balanced balance will not rotate or dip to either side. Because the two objects has the same force acting downwards, and the distance from the pivot is the same.

A balanced balance

What I found difficult about what I have studied is actually the identification of forces. Sometimes, when the questions get complex, cannot solve in simple steps and requires multiple steps, I become confused, or even anxious. It is easy to misidentify the forces and how they affect the system.
However, the above mistake can be solved by doing problems and analyzing different types of questions.

The hard part of torque is when the beam becomes slanted, it is easy to misidentify and calculate the distance from the pivot point to the rope. Especially when the rope is not perpendicular to the beam.
I solved the above hardship also by doing more problems and analyzing different types of questions. I found out that physics is learned the best by actually doing work, reading notes over and over again would not improve problem solving skills.

My problem solving skills got better through the two months of studying. I learned to analyze and find out useful information out of the diagram. I became more confident about my problem solving skills, also by doing different types of questions I felt I'm now more insightful.

I'm now comfortable with questions that involve multiple steps or require great logic. Since physics is not only about doing problems, I have also applied the knowledge I have learned to rigging tackles and explaining mechanical advantages of pulleys in sea cadets.

Overall, I really appreciate the boost in knowledge and problem solving skills that dynamics and equilibrium had brought to me. I am now more confident to learn harder and more logical concepts of Physics.