inertia and newton’s laws

what is inertia?

inertia is the tendency for motion to remain unchanged, meaning objects at rest stay at rest, and objects moving at a steady speed will keep moving at that speed until acted upon by a resultant force

how does inertia relate to an object’s mass?

an object’s inertial mass measures how difficult it is to change the velocity of the object

how can inertial mass be calculated?

inertial mass can be found using newton’s second law (f = ma), and rearranging it gives m = f/a, meaning inertial mass is equal to force over acceleration

what does newton’s third law state?

newton’s third law states that when two objects interact, the forces they exert on each other are equal and opposite

can forces in newton’s third law cancel each other out?

no, because the forces are acting on different objects, so they don’t cancel each other out

why does skater a accelerate more than skater b when they push off each other?

skater a accelerates more because she has a smaller mass, according to the formula a = f/m

what happens when a man pushes against a wall?

the man exerts a force on the wall, and the wall exerts an equal and opposite force on the man, as described by newton’s third law

why is the book resting on the ground in equilibrium?

the weight of the book is balanced by the contact force, but this is not an example of newton’s third law because the forces are different types and both act on the book

how does equilibrium relate to newton’s third law?

in equilibrium, the forces acting on an object, like the book, are equal but of different types, so they don’t t follow newton’s third law because they don’t t act on separate objects