Rigid body mechanics Intro

Front

If a door doesn’t bend when you push it, why do we still call it a rigid body and not a “stubborn door”?

Back

Rigid body = ideal assumption: no bending/stretching. Real doors bend a tiny bit, but we ignore it for physics!

Front

What’s the difference between pushing your friend on a swing at the chains vs. at the seat?

Back

Both are forces, but one creates more torque because of longer distance from pivot.

Front

Why is it easier to push open a door at the handle than near the hinge? (Or should carpenters move handles closer to hinges?)

Back

Torque = Force × Distance from axis. Farther = stronger effect.

Front

If “mass” is like a child saying “Don’t push me in a straight line,” then what does moment of inertia say when you try to spin them?

Back

“I resist rotation!” → It’s the rotational twin of mass.

Front

If two ice-skaters of the same weight spin, one with arms stretched out and one with arms tucked in, who spins faster? Why?

Back

Moment of inertia smaller when arms tucked → spin faster (conservation of angular momentum).

Front

Is “rotatory motion” just circular motion with extra drama?

Back

No → Circular motion = one point goes in a circle. Rotatory motion = whole object spins about axis.

Front

Why does a pizza chef spin dough in the air — is it just for show or for physics?

Back

Spinning dough flattens out because of angular motion + conservation of angular momentum.

Front

If a seesaw balances with a fat cat close to the pivot and a skinny dog far away, who is winning the physics game?

Back

Both balance because torques equalize: mass × distance = mass × distance.

Front

Why is pushing a car the same as applying force, but turning a steering wheel needs torque? Aren’t they the same thing?

Back

Force = straight push/pull. Torque = twist about an axis. Different but connected.

Front

If Earth is spinning and we’re all sitting on it, why don’t we fly off like toys on a merry-go-round?

Back

Because gravity provides the centripetal force — keeping us glued.