Explain
Newton's laws of motion in terms of a supermarket trolley
Newton's laws of motion are essentially the physics of pushing a wonky supermarket trolley through a crowded aisle at Tesco on a Bank Holiday Monday.
The first law is why your trolley remains perfectly stationary in the entrance foyer, blissfully ignoring your desperate attempts to nudge it until you apply the force of a frantic dash towards the Reduced section. It prefers to remain in its state of rest, much like a teenager on a Sunday morning, and once it is moving at a constant velocity, it will happily keep drifting into a display of festive biscuits unless you act as the resultant force to correct its course.
The second law is the simple realisation that the acceleration of your trolley is directly proportional to your panic and inversely proportional to how many crates of own-brand lager you have stacked in it. If you load it with ten kilograms of potatoes, your acceleration is pitiful, and trying to shove it into a sudden turn results in a humiliating screech of rubber on lino. Force equals mass times acceleration, which is why your trolley always feels twice as heavy when you are trying to reach the checkout before the queue hits the cereal aisle.
The third law is the moment you collide with a lady's floral shopping bag. Your trolley pushes on the bag, and the bag pushes back on your trolley with a force exactly equal in size and opposite in direction. The two forces act on different things, which is why the bag swings sideways while you just get a jolt, an apologetic wince and a silent, passive-aggressive dance of recoil.
Where the analogy breaks downA supermarket trolley wheel has a mind of its own and will refuse to move in a straight line regardless of any amount of force applied.