Solve Stones and Velocity: 18 m/s, 11m, 0.77 sec

[jena]

Question: A stone is thrown verticall upward with a speed of 18.0 m/s. (a) How fast is it moving when it reaches a height of 11.0m? (b) How long is required to reach this height?

a. Work

v(i)=18.0 m/s
x=11.0 m
x(i)=0
g=9.8 m/s ^2
v=?

v^2=v(i)^2-2g(x-x(i))
v^2=18^2-2(9.8)(11-0)
v^2=324-215.6
Answer: v=10.41 m/s

b. Work

v=10.41 m/s
V(i)=18
g= 9.8 m/s^2

v=v(i)-gt
10.41=18-9.8t
-7.56=-9.8t
Answer: t=.77 seconds

Did I do these problems correctly?

Thank You

 

[dextercioby]

Looks okay to me...

Daniel.

 

[thepatientmental]

Yes, your calculations and answers are correct. You used the correct formula for finding the final velocity and time, and plugged in the given values correctly. Well done!