Forces and motion flashcards

Forces and motion covers how forces cause objects to accelerate, decelerate or change direction. Students must understand scalar and vector quantities, and be able to use equations linking speed, velocity, acceleration, distance and time. Newton's three laws of motion are central: the first explains why objects stay at rest or move at constant velocity unless a resultant force acts; the second links force, mass and acceleration; the third describes action-reaction pairs. Students should interpret distance-time and velocity-time graphs, calculate areas and gradients, and understand stopping distances. Momentum, inertia and the effect of friction and air resistance are also key. The topic links forces to everyday situations such as vehicle safety and falling objects reaching terminal velocity.

1. Card 1

   What is the difference between speed and velocity?

   Speed is a scalar quantity with magnitude only. Velocity is a vector quantity with both magnitude and direction.

2. Card 2

   State the equation linking acceleration, change in velocity and time.

   Acceleration (m/s²) = change in velocity (m/s) divided by time (s). Written as a = (v - u) / t.

3. Card 3

   What does the gradient of a distance-time graph represent?

   The gradient of a distance-time graph represents the speed of the object at that point.

4. Card 4

   What does the area under a velocity-time graph represent?

   The area under a velocity-time graph represents the distance travelled by the object during that time interval.

5. Card 5

   State Newton's First Law of motion.

   An object remains at rest or moves at a constant velocity unless acted upon by a resultant force.

6. Card 6

   State Newton's Second Law of motion as an equation.

   Force (N) = mass (kg) x acceleration (m/s²), written as F = m x a. A larger resultant force produces a greater acceleration.

7. Card 7

   What is Newton's Third Law of motion?

   For every action force, there is an equal and opposite reaction force acting on a different object.

8. Card 8

   What is meant by the resultant force on an object?

   The resultant force is the single force that has the same effect as all the individual forces combined, found by adding vectors.

9. Card 9

   What is terminal velocity and why does a falling object reach it?

   Terminal velocity is reached when air resistance equals the weight of the object, so the resultant force is zero and acceleration stops.

10. Card 10

    What is the equation for momentum?

    Momentum (kg m/s) = mass (kg) x velocity (m/s), written as p = m x v. Momentum is a vector quantity.

11. Card 11

    What are the two components of stopping distance for a vehicle?

    Stopping distance = thinking distance (distance travelled during driver reaction time) plus braking distance (distance during braking).

12. Card 12

    What is inertia?

    Inertia is the tendency of an object to resist changes to its state of motion. Greater mass means greater inertia.

• Many students confuse mass and weight, forgetting that weight is a force measured in newtons while mass is measured in kilograms.
• Students often think that a moving object needs a constant force to keep it moving, ignoring Newton's First Law which states no resultant force is needed for constant velocity.
• When reading velocity-time graphs, students sometimes calculate the gradient instead of the area when asked for distance travelled, mixing up what each feature represents.

Planning your revision? Read how to revise GCSE Physics, or make cards from your own notes with the notes to flashcards tool.