What Can Be 0 for a Moving Body? The Physics You Didn't Expect
A body in motion... but something's still zero?
At first glance, this sounds like a paradox, right? If something is moving, shouldn’t everything — speed, momentum, energy — be non-zero?
Well, nope. In physics, it's entirely possible (and common) for a moving body to have certain quantities equal to zero. And that’s what makes this question surprisingly interesting.
Let’s break it down — and hey, we’ll skip the dry textbook lingo (mostly).
Quantity #1: Displacement can be zero (even with motion!)
Wait, what? How can something move and not be displaced?
Displacement is not the same as distance. That’s the key here.
If a body starts and ends at the same point, its displacement is zero — even if it moved the entire time.
Example:
A person jogs around a circular track and ends up exactly where they started. Total distance = maybe 400 meters.
Displacement? 0. Because there's no change in position.
That messed with my head the first time I heard it in high school. I actually argued with the teacher (and yeah… I was wrong).
Quantity #2: Net force can be zero (Newton’s first law says hi)
Moving with no force? Sounds fake, but it’s physics.
If an object moves at constant velocity, there’s no net force acting on it. That doesn’t mean there are no forces at all — just that they cancel each other out.
Think of a hockey puck gliding on ice. No one’s pushing it anymore, but it keeps sliding. That’s zero net force in action.
So yeah, a moving object can totally have net force = 0.
Quantity #3: Acceleration can be zero
Constant speed = zero acceleration
Acceleration measures change in velocity. So if an object is moving at a constant velocity, there’s no acceleration. Simple as that.
That includes things like:
A car using cruise control on a straight highway
A satellite in uniform circular motion (well… almost, that one’s a bit trickier)
In all those cases:
Motion = yes
Acceleration = nope
And guess what? If acceleration is zero, and net force is zero, Newton would be proud.
Quantity #4: Relative velocity can be zero
Depends on your frame of reference
Here’s one of those “ah-ha!” physics moments.
Imagine you're sitting in a train moving at 80 km/h. The person sitting next to you? Also moving at 80 km/h.
But relative to you, their velocity is zero.
So, even though you're both flying down the tracks, your relative motion = none.
Same thing happens with airplanes, cars, boats... physics is all about perspective.
But what about momentum or kinetic energy?
Now here’s where things flip.
If a body has mass and is moving, then:
Momentum (p = mv) ≠ 0
Kinetic energy (KE = ½mv²) ≠ 0
These are directly tied to velocity — so unless you’re going zero speed, these quantities won’t be zero.
No tricks here.
Unless... you're in a massless theoretical particle world, which, yeah, let’s not go there today.
Final thoughts: So, what can be 0 for a moving body?
Let’s recap it clean and simple:
| Quantity | Can it be zero while moving? |
|---|---|
| Displacement | Yes (in circular or return paths) |
| Net Force | Yes (constant velocity) |
| Acceleration | Yes (no change in velocity) |
| Relative velocity | Yes (depends on reference frame) |
| Momentum | Nope |
| Kinetic energy | Nope |
So next time someone says, “If it’s moving, nothing can be zero” — you can hit them with displacement, net force, AND acceleration all in one breath. Physics flex unlocked.
And honestly? That’s kinda cool.
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How Tall Should a 12 Year Old Be? We can only speak to national average heights here in North America, whereby, a 12 year old girl would be between 137 cm to 162 cm tall (4-1/2 to 5-1/3 feet). A 12 year old boy should be between 137 cm to 160 cm tall (4-1/2 to 5-1/4 feet).
How tall is a average 15 year old?
Average Height to Weight for Teenage Boys - 13 to 20 Years
| Male Teens: 13 - 20 Years) | ||
|---|---|---|
| 14 Years | 112.0 lb. (50.8 kg) | 64.5" (163.8 cm) |
| 15 Years | 123.5 lb. (56.02 kg) | 67.0" (170.1 cm) |
| 16 Years | 134.0 lb. (60.78 kg) | 68.3" (173.4 cm) |
| 17 Years | 142.0 lb. (64.41 kg) | 69.0" (175.2 cm) |
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