a ball is dropped from the top on an 80-m high building. what speed does the ball have in falling 3.5 s?
I keep getting the answer 34.3m/s but it is counted wrong. I found an answer on Chegg that say 29.4 m/s but I can't figure out how they are getting that answer.
v = g t
= 9.8 * 3.5 = 34.3 m/s
I agree with you.
To find the speed of the ball at a particular time, you can use the equation of motion for free-falling objects:
v = u + gt
Where:
v = final velocity or speed of the ball
u = initial velocity (which is zero since the ball is dropped)
g = acceleration due to gravity (which is approximately 9.8 m/s^2)
t = time
In this case, the ball is dropped from rest, so the initial velocity u is 0 m/s. The acceleration due to gravity is -9.8 m/s^2 because it acts downward. Since the ball is falling, we consider the acceleration as negative.
Now let's calculate the speed of the ball when it has fallen for 3.5 seconds:
v = 0 + (-9.8) * 3.5
v = -34.3 m/s
The negative sign indicates that the velocity is downward.
You mentioned that you found an answer of 29.4 m/s on Chegg. It's possible that the answer given on Chegg is incorrect, or there may be more information or context provided that contributes to a different value. It's always important to consider the given information and the equations being used.