Question

Newton's First Law: InertiaYou are riding in the car with your grandfather, and he turns left. Why do you shift to the right?It takes you a moment to catch up with the new velocity of the car.You have more inertia than the car, so it takes longer for you to turn left.You had been sitting at rest until the force of the turn set you in motion.The car continued in the same velocity, but you had a different inertia.

Answer 1

Short answer: because of inertia (Newton’s 1st law) — your body tends to keep moving in the original direction, so when the car turns left you continue straight for a moment and thus slide toward the right relative to the car until the car (seat/door, friction) exerts a sideways force on you.

About the choices:
- "It takes you a moment to catch up with the new velocity of the car." — Correct in spirit: you need a sideways force to change your motion, so you lag briefly.
- "You have more inertia than the car, so it takes longer for you to turn left." — Incorrect. Inertia depends on mass; the car has far more mass (more inertia). The effect is not because you have more inertia than the car.
- "You had been sitting at rest until the force of the turn set you in motion." — Partly correct if “at rest” means relative to the car: a sideways force is needed to give you the new lateral velocity.
- "The car continued in the same velocity, but you had a different inertia." — Incorrect. The car changed direction because of forces from the road; "different inertia" is misleading.

If you want the physics words: in an inertial frame you tend to move in a straight line (inertia). In the car’s rotating/non-inertial frame it feels like a fictitious force pushes you to the right; physically, the seat/door must supply a centripetal force to make you follow the turn.