Thread: quadratic

hi, need help

A window washer drops a squeegee from a scaffold 100 m off the ground. The
relationship between the height of the squeegee (h), in metres, and the length of time
it has been falling (t), in seconds, is given by h = 100 − 5t2.
a) When does the squeegee pass a window 30 m off the ground?
b) How long does it take for the squeegee to hit the ground?

thanks!

Originally Posted by smmmc

hi, need help

A window washer drops a squeegee from a scaffold 100 m off the ground. The
relationship between the height of the squeegee (h), in metres, and the length of time
it has been falling (t), in seconds, is given by h = 100 − 5t^2.
a) When does the squeegee pass a window 30 m off the ground?
b) How long does it take for the squeegee to hit the ground?

thanks!

For squeegee to be 30 metres above the ground



Hence


Thus
Hence
Since time cannot be negative its taken as


For squeegee to hit the ground its height should be 0
so


Thus


Hence


Hence

Originally Posted by ADARSH

For squeegee to be 30 metres above the ground



Hence


Thus
Hence
Since time cannot be negative its taken as


For squeegee to hit the ground its height should be 0
so


Thus


Hence


Hence

hey how did you get the 20 in this

Originally Posted by smmmc

hey how did you get the 20 in this

By mistake