Study Notes
Newton's laws of motion describe the relationship between a body and the forces acting upon it, and its motion in response to those forces.
- Newton's First Law — A body will continue its state of rest or uniform motion in a straight line unless an external force changes that state. Example: A book on a table stays at rest until someone pushes it.
- Newton's Second Law — The resultant force acting on a body is proportional to the rate of change of momentum of the body. F=ma Example: A car accelerates faster if a greater force is applied.
- Newton's Third Law — Every action has an equal and opposite reaction. Example: When you jump off a small boat, the boat moves in the opposite direction.
- Thrust — A force applied by a rod pushing outwards. Example: A rod pushing a lamp post to prevent it from falling.
- Tension — A force in a string or rod pulling inwards. Example: The tension in a tow rope pulling a trailer.
Exam Tips
Key Definitions to Remember
- Newton's First Law
- Newton's Second Law
- Newton's Third Law
- Thrust
- Tension
Common Confusions
- Mixing up thrust and tension
- Misapplying Newton's second law to non-linear motion
Typical Exam Questions
- What is the acceleration of a system of connected particles? Use F=ma to solve for acceleration.
- How do you calculate the tension in a string? Apply Newton's second law to each particle and solve.
- What happens to the forces when a string passes over a pulley? The tension remains the same, but the direction can change.
What Examiners Usually Test
- Application of Newton's laws to solve problems
- Understanding of forces in systems with rods and strings
- Ability to calculate acceleration and tension in connected systems