Stuck On a Question. Please help. (1 Viewer)

[ISL1805]

A stone is let fall from a tall building and 1 second later another stone is projected vertically
downwards with a velocity of 20 m/s. When will the second stone overtake the first?

This is from the 3 unit mathematics jones and couchman book 2 textbook, chapter 26.3, question 9. The answer comes out to 1.48 seconds

I keep on getting 1.45 somehow, if anyone can help me get this answer it would be much appreciated.

 

[fan96]

A stone is let fall from a tall building and 1 second later another stone is projected vertically
downwards with a velocity of 20 m/s. When will the second stone overtake the first?

This is from the 3 unit mathematics jones and couchman book 2 textbook, chapter 26.3, question 9. The answer comes out to 1.48 seconds

I keep on getting 1.45 somehow, if anyone can help me get this answer it would be much appreciated.

How did you work out 1.45?

 

[Drongoski]

For stone-1: x(t) = 0.5gt²

For stone-2: x(t) = 0.5gt² + (20-g)t +(.5g-20)

When the 2 are equal:

(20-g)t = 20 - 0.5g ==> t = (20 - 0.5 x 9.8)/(20 - 9.8) = 1.48039 . . . sec

 

[ISL1805]

Thank you very much for your help

 

[ISL1805]

Must of made a error in my calculations.