SP2 Flashcards
What is a resultant force?
The single force that shows the overall effect of all the forces acting on an object
How do you calculate resultant force if two forces act in opposite directions?
Subtract the smaller force from the larger one (direction of the larger force).
State Newton’s First Law of Motion
An object will remain at rest or move at a constant speed in a straight line unless a resultant force act on it
What do we call the tendency of objects to resist changes in motion?
Inertia.
What is the difference between mass and weight?
Mass: Amount of matter (kg, scalar)
Weight: Force due to gravity (N, vector) → Weight = mass × gravitational field strength (W=mg)
Calculate the weight of a 5kg object on Earth (g=9.8 N/kg).
W = 5 × 9.8 = 49 N
State Newton’s Second Law
F = ma (Resultant force = mass × acceleration)
A 2kg object accelerates at 3 m/s². What resultant force acts on it?
F = 2 × 3 = 6 N
State Newton’s Third Law
When two objects interact, they exert equal and opposite forces on each other
Give an example of Newton’s Third Law pair
Rocket pushing gases down, gases pushing rocket up.
What is the formula for momentum?
p = mv (momentum = mass × velocity)
Units: kg m/s
A 0.5kg ball moves at 4 m/s. Calculate its momentum.
p = 0.5 × 4 = 2 kg m/s
What factors affect thinking distance?
Speed, reaction time, distractions, tiredness, drugs/alcohol
What factors affect braking distance?
Speed, vehicle mass, road conditions, brake/tire quality
What energy transfer happens during braking?
Kinetic energy → Thermal energy (due to friction)
Why does braking distance increase quadratically with speed?
KE = ½mv² → Double speed = 4× KE → 4× distance needed to stop.
How do seatbelts/crumple zones reduce injury?
Increase stopping time → Reduce force (F = Δp/t).
