Hey, I think it could be -9.8 if Chad decides to define upwards motion as positive. So the answer could end up as -78.9m meaning that the ball has dropped down below the initial ground (0m). Here, I think Chad just decided to define the downward motion as positive.
My apologies Joseph for not getting to this sooner and probably not in time for your exam. The value of g is properly -9.8. But if the displacement, velocity, and acceleration are all downward, you'd be plugging in negative values for all three which would work out exactly the same as if you plugged in positive values for all three. But the key is that all three are downward. If that weren't the case than which are positive and which are negative would be vital to getting a correct answer. As students often mess this up your professor is playing it safe (which is smart and probably the way to go). But some professors don't play it safe which is why I took the time to explain when g has to be -9.8 and when you can get away with simply using 9.8. Hope this helps and Happy Studying!
Physics is tough on the old grey matter cells but this guy makes it bearable.
Thanks Wesley as that is my goal! 🙂
Your videos are wonderful. Thanks for making them available for all
You're very welcome and so glad you're finding them helpful!
studying for physics final & these were exactly what I needed help with! TY
Awesome Kelly and you're welcome! Best wishes on your final exam!🙂
Great Practice Session! I am going to bloat this exam out of the water!
BLOAT that exam! :-) Or blast it, whichever gets you the best score!!!
why positive 9.8
why not - 9.8 since it's going downward
it will be 0 if we were talking about x-axis correct me if I'm wrong
Thanks
Hey, I think it could be -9.8 if Chad decides to define upwards motion as positive.
So the answer could end up as -78.9m meaning that the ball has dropped down below the initial ground (0m).
Here, I think Chad just decided to define the downward motion as positive.
He gives a better explanation @4:00
Hyun RDH
I have my exam on Monday 😱
Hyun RDH
My professor keeps saying that g is always -9.8
My apologies Joseph for not getting to this sooner and probably not in time for your exam. The value of g is properly -9.8. But if the displacement, velocity, and acceleration are all downward, you'd be plugging in negative values for all three which would work out exactly the same as if you plugged in positive values for all three. But the key is that all three are downward. If that weren't the case than which are positive and which are negative would be vital to getting a correct answer. As students often mess this up your professor is playing it safe (which is smart and probably the way to go). But some professors don't play it safe which is why I took the time to explain when g has to be -9.8 and when you can get away with simply using 9.8.
Hope this helps and Happy Studying!
IM SO CONFUSED ON THE FORMULAS