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# 9.8ms^-2 (unsure of how we get 'per-second per-second' and what this means)

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1. Howdy .

So gravity has 9.8ms^-2

What does metres per-second, per-second mean when explaining this?

As with acceleration, I get that 4ms^-1 means an object is travelling four metres every second.

Thanks
2. (Original post by makin)
Howdy .

So gravity has 9.8ms^-2

What does metres per-second, per-second mean when explaining this?

As with acceleration, I get that 4ms^-1 means an object is travelling four metres every second.

Thanks
For your example then the velocity of the object increases by 4 m/s every second i.e if it starts at 0 m/s at t = 0 (v(0)) then v(1) = 4 m/s, v(2) = 8 m/s, v(3) = 12 m/s etc.
3. Acceleration is the change in velocity/time
Velocity is m/s and time is s
That means m/s (or ms^-1)/ s
Hence ms^-2
4. (Original post by makin)
Howdy .

So gravity has 9.8ms^-2

What does metres per-second, per-second mean when explaining this?

As with acceleration, I get that 4ms^-1 means an object is travelling four metres every second.

Thanks
Each second the velocity increases by 4m/s
5. The speed increase every second, so you know that after 1 second a object is falling at 9.81m/s
Acceleration is the change in velocity/time
Velocity is m/s and time is s
That means m/s (or ms^-1)/ s
Hence ms^-2
Ah, that makes sense. Thanks

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