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  • Writer's pictureTerence Pang

Commonly asked A Level Physics Question on Circular Motion - based on YIJC Tutorial Question 4

Updated: Jan 30

If you're having issues solving A level Physics circular motion questions, then watching this video may be good for you. Learn the proper strategies and excel better in your studies.


In this video, we analyse a question on circular motion that can be commonly seen in many school papers and A level exams.


The challenge to circular motion problems is that it involves a multitude of concepts and applying them in several steps in order to arrive at the answer.


Step-by-Step video to Show How Circular Motion Questions can be Solved


Below is a video where we work on a circular motion question very commonly found in many test papers. The strategy would be to:

  1. Draw a free body diagram

  2. Resolve forces in vertical and horizontal direction using the laws of trigonometry and vector resolution

  3. Apply newton's 2nd law when resolving the forces - taking note that the horizontal component involves the centripetal force so we will need to use the centripetal force formula. There are 2 formula for centripetal force so we will use the one that has the angular speed term in it.


Watch the video for a detailed step-by-step solution.



Background to A Level Physics - Circular Motion


Circular motion is a fundamental concept in A Level Physics, particularly as outlined by the Singapore Examinations and Assessment Board (SEAB) syllabus. Here's an overview that might be helpful, focusing on key aspects that are typically included in the A Level curriculum.

1. Basic Concepts of Circular Motion

  • Definition: Circular motion refers to the movement of an object along the circumference of a circle at a constant speed.

  • Velocity: The object has a constantly changing velocity due to its direction changing at every point, even if the speed remains constant.

  • Centripetal Force: This is the net force causing the circular motion, directed towards the center of the circle.

2. Mathematical Formulation

  • Centripetal Acceleration: a=v^2/r where v is the velocity and r is the radius of the circular path.

  • Centripetal Force: Fc=ma = mv^2/r = mrw^2​, where m is the mass of the object and w is the angular velocity

3. Examples of Circular Motion in Everyday Life

  • Planetary orbits.

  • Artificial satellites orbiting the Earth.

  • Vehicles turning around a curve.

4. Newton's Laws and Circular Motion

  • First Law: The tendency of objects to maintain their state of motion (inertia) plays a crucial role in understanding why centripetal force is necessary.

  • Second Law: The centripetal force is the result of the acceleration towards the center of the circle.

5. Applications in Problem Solving

  • Students are often asked to solve problems involving calculating the centripetal force, the velocity of an object in circular motion, or the period of rotation.

  • Real-world problems may include calculating the forces acting on a vehicle on a curved track or the tension in a string of a pendulum.

6. Common Misconceptions

  • One common misconception is that centrifugal force (an apparent force observed in a rotating reference frame) is the same as centripetal force.

  • The misconception that an object in circular motion has constant velocity due to constant speed, neglecting the vector nature of velocity.

7. Integration with Other Topics

  • Linking circular motion to topics like gravitation, energy, and momentum.

  • Demonstrating how circular motion principles are foundational in understanding complex systems in astrophysics and engineering.

8. Assessment and Evaluation

  • Typical assessments involve quantitative problems, conceptual questions, and practical experiments.

  • The emphasis is on applying theoretical knowledge to practical situations and problem-solving skills.



A Level Physics: (Left) Ball in a circular motion – rope provides centripetal force to keep the ball in a circle (Right) Rope is cut and the ball continues in a straight line with the velocity at the time of cutting the rope, in accord with Newton's law of inertia, because centripetal force is no longer there.
A Level Physics : (Left) Ball in a circular motion – rope provides centripetal force to keep the ball in a circle (Right) Rope is cut and the ball continues in a straight line with the velocity at the time of cutting the rope, in accord with Newton's law of inertia, because centripetal force is no longer there.


The SEAB A Level Physics syllabus aims to provide students with a comprehensive understanding of circular motion, blending theoretical knowledge with practical applications.


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