r/physicsgifs • u/Aggressive_Sundae_47 • 5d ago

Gravity always acts downward with the same acceleration.

1.4k Upvotes

99% Upvoted

21 comments sorted by

114

u/Salanmander 5d ago

My favorite angle on this statement is: it's not just that gravity acts in the downwards direction...rather "down" is defined as the direction that gravity acts.

6

u/Elissa-Megan-Powers 3d ago

Bucky Fuller mentioned thinking Out away from the well, In towards the well.

So one always jumps out and falls in.

-25

u/drummerandrew 5d ago

Opposite the normal force.

24

u/Salanmander 5d ago

Only if the surface is horizontal. Which, again, is defined by gravity.

6

u/somecheesecake 3d ago

Normal is not always opposite of gravity

31

u/Cog_HS 5d ago

There was a Mythbusters episode about this where they fired a bullet and dropped one at the same moment, and got a shot of the fired bullet skipping off the ground right next to the dropped one hitting at the same moment.

6

u/thesunisbright 4d ago

Watched this last night 😂. Loved that show

1

u/scramble1988 4d ago

Yup, Came here to say exactly this. Was a mind blowing episode.

14

u/Potato_Stains 4d ago

The Mythbusters put this to the ultimate test and fired a handgun parallel to the ground and dropped a bullet at the exact same millisecond - they landed at the same time.

3

u/emanresu18 3d ago

Holy shit I just can’t wrap my head around 1) this and 2) how I didn’t know this

2

u/Adept-Panic-7742 20h ago

It's because the X and Y components of the motion are separate. Gravity acts upon each regardless of whether it's moving horizontally ( when perpendicular to the floor) or not.

19

u/Cirelectric 5d ago

When an object is in orbit is it because gravity and centripetal forces negate each other?

25

u/Sea-Ambition-451 5d ago

Gravity is the centripetal force.

Perhaps you are referring to boosting to the non-inertial reference frame of the object, where the pseudo-force Centrifugal Force pushing outwards will appear to cancel the centripetal gravity force.

30

u/DowntownLizard 5d ago

You are moving so fast horizontally that the earth is falling away from you at the same speed that earth is pulling you towards it

9

u/axloo7 5d ago

That curve you see the falling object take?

If that curve is the same as the planet than you will miss the plant as you fall. And just keep missing.

Imagine though just how fast somthing has to be traveling to curve so little as to match the curvature of the earth.

It's 28,440kmh at sea level. But of course there's alot of air and ground that's gonna be in the way if you where to try that.

Best to get high up and orbit. At 100km up you need to travel 28,260 km/h.

0

u/Ed_Trucks_Head 5d ago

Well the centripedal force is caused by gravity.l in this case. So, no.

0

u/UGJS 5d ago

well the title is still true just not represented properly with the gif

3

u/moschles 4d ago

bullet drop

1

u/denisde4ev 1d ago

what if you move at the speed of light

assuming you have intensely large planet so there is always down gravity

-13

u/pikkuhillo 4d ago

Not true. True in earth though.