Forces, Motion & Momentum
A force is a push or pull that acts on an object due to its interaction with another object, capable of changing its speed, direction, or shape. This guide covers scalar vs vector quantities, resultant forces, Newton's three laws of motion, terminal velocity, stopping distances, and conservation of momentum.
- Velocity
- The speed of an object in a given direction (a vector quantity).
- Acceleration
- The rate of change of velocity, measured in m/s².
- Terminal Velocity
- The constant maximum velocity reached by a falling object when the resistive forces balance the driving force (e.g., weight).
Forces, Motion & Momentum: Wave Equation (v = fλ) & Force Vector (F = ma) Simulator
Adjust physical variables on the sliders below to see real-time changes in wave geometry, resultant forces, and acceleration.
F_net = 80 N − 25 N = 55 NAcceleration: a = F_net ÷ m = 55 ÷ 10 = 5.50 m/s²Key Concepts & Exam Definitions (5)
- Velocity
- The speed of an object in a given direction (a vector quantity).
- Acceleration
- The rate of change of velocity, measured in m/s².
- Terminal Velocity
- The constant maximum velocity reached by a falling object when the resistive forces balance the driving force (e.g., weight).
- Momentum
- The product of mass and velocity (p = mv), measured in kg m/s.
- Hooke's Law
- The extension of an elastic object is directly proportional to the force applied, provided the limit of proportionality is not exceeded.
Quick-Fire Flashcards (5)
Click any card to check the answer, then mark it as Known to track your progress.
What is the formula linking force, mass, and acceleration?
Is force a scalar or vector quantity?
What is the formula for calculating momentum?
What happens to the momentum in a closed system during a collision?
What factors affect a driver's thinking distance?
Exam-Style Questions & Mark Schemes (3)
Write or think through your answer first, then click Check Mark Scheme to see the exact points examiners award marks for.
- Q1
A car of mass 1000 kg accelerates at 2 m/s². Calculate the resultant force acting on it.
Click “Check Mark Scheme” to compare your answer, Force = mass × acceleration = 1000 × 2 = 2000 N.
- Q2
A 50 kg skater moves at a velocity of 4 m/s. What is their momentum?
Click “Check Mark Scheme” to compare your answer, Momentum = 50 × 4 = 200 kg m/s.
- Q3
Explain why a falling skydiver eventually reaches a constant speed.
Click “Check Mark Scheme” to compare your answer, As they fall and gain speed, air resistance increases. Eventually, air resistance equals their weight, so the resultant force is zero, resulting in no further acceleration (terminal velocity).
Common Exam Questions (3)
What is a resultant force?
The resultant force is the single overall force that has the same effect on an object's motion as all the individual forces acting on it combined, taking direction into account.
What is the difference between scalar and vector quantities?
A scalar quantity has magnitude (size) only, such as speed, distance, mass, or energy. A vector quantity has both magnitude and an associated direction, such as velocity, displacement, force, acceleration, or momentum.
What is stopping distance?
Stopping distance is the total distance a vehicle travels between the driver first spotting a hazard and the vehicle coming to a complete rest: Stopping Distance = Thinking Distance + Braking Distance.
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