Since their launch in 1977, the Voyagers have been coasting - moving The Sun than Earth is, more than 3 times the Sun-Neptune distance. They are now both about 100 times further from To visit the gas-giant planets Jupiter and Saturn. The Voyager 1 and 2 space probes were launched in 1977, Though we’ll discuss the distinction in more detail after we talk about This is called a concussion.Ī common theme from the above examples is that inertia often feels likeĪ force, in the opposite direction to the actual force. In bruising, swelling, and disruption of brain function. Moving, causing it to ram into the inside of your skull, resulting Your skull stops suddenly, but your brain keeps While riding a skateboard without a helmet, you fall and your head.

If not, you will continue through the windshield and be stopped If you have your seatbelt on, the seatbelt will do the You will continue moving at your original velocity until somethingĭoes stop you. The tree isn’t exerting a force on your body, however, and The car comes toĪ sudden stop because the tree is exerting a very large force on theĬar.

Imagine you are in a car and crash into a tree.

Watch this video from CNN about testing conducted by the Insurance Institute for Highway Safety. Is your body is being accelerated forward and your head is being leftīehind. If your head is snapped backwards, but what’s really happening If there is no headrest, your head will be acceleratedįorward by your very overstetched and bent neck. Your body isĪccelerated forward by the force of the seat, but your head wants to

Imagine you are in a stopped car (say, at a red light) and anotherĬar strikes yours from behind, you may suffer whiplash.

Here are some consequences of inertia that I hope you never experience. The ball lands in your hand because, when it was in the air, its inertiaĬarried it forward at the same speed it had when you were holding it. To an observer standing by the road, however, Straight down back into your hand, just as it would if you and theĬar were stationary. To you, it appears to rise straight up, stop, and fall

You are in a vehicle moving with constant velocity, and toss a ball.

(Iĭid this once with a very expensive computer monitor on a cart. On the cart to start or stop it, the object on top may fall off.

You are rolling a cart with an object on top of it.

Or the bottle opening narrow, it might not work.) It to keep going and come out of the bottle. Shake the bottle, bringing the upside-down bottle towards the plateĪnd stopping it suddenly, hoping the inertia of the ketchup will cause

You are trying to get ketchup out of a bottle.

Actually, the seatbelt is exerting a backwards Keep going at its original speed, and you feel like you are being pushedįorward, into the seatbelt.

You are in a car that comes to a sudden stop.

You know about inertia from your everyday experience.

The idea of inertia wasn’t discovered by Newton, despite beingĬalled “Newton’s First Law”. The invention of the wheel, while not removing frictionĮntirely, greatly reduces friction and makes it easier to keep things When friction is reduced to insignificance, inertia becomes much moreįor example: a hockey puck sliding on an ice rink, or the puck on anĪir hockey table. Is because there almost always is an “outside force” - friction. The reason most things in our lives do NOT keep moving forever To a stop boxes slid on the floor come to a rest unless you keep pushing In our everyday experience, thingsĭon’t keep moving unless something pushes them. You’ve probably heard of this before, and may even think that Other synonyms: tug, nudge, poke,Īlternate phrasing of Newton's 1st Law: An object cannot change Note that this statement is meaningless unless you know what a force Line with constant speed, unless acted upon by an outside force. Introduction The traditional phrasing of Newton'sįirst Law of Motion is this: An object at rest will remainĪt rest (forever!), and an object in motion

First law of motion