A man jumps with a speed v(xi) from a roof at a height of 10m. He falls 3m from the wall. What is its initial velocity v(xi)?

Problem: a man jumps with a speed v(xi) from a roof at a height of 10m. He falls 3m from the wall. What is its initial velocity v(xi)?
1. I first calculate the time from the jump with the formula: y(f)-y(i) = v(yi)t-1/2gt². v(yi) = 0 then t=1.43s.
2. I plug this value into the formula x(f)-x(i)=v(xi)t-1/2(9.81)(1.43)² v(xi) = 9.11 m/s.
My question: is (2) correct?

Asker: Fund, 63 years old

Answer

The fall time is indeed 1.43 seconds.

However, the second part of your solution is wrong because in the x-direction there is no acceleration, because no force, (if we neglect air resistance). The gravitational term with g in it is therefore not present in the x-direction. So there it is basically simpler than what you do:

x

So we fill in : 3 = v(xi) . 1.43

so that v(xi) = 2.10 m/s

Answered by

prof.dr. Paul Hellings

Department of Mathematics, Fac. IIW, KU Leuven

Catholic University of Leuven
Old Market 13 3000 Leuven
https://www.kuleuven.be/

.

Recent Articles

Practical experience Toyota RAV4: What do owners think of their car?

Big Toyota not only popular with thieves guildYou recently read on this site that the Toyota RAV4 is the most stolen car in the...

Green Flags: This indicates a good relationship

Photo: CC0 / Pixabay / StockSnap Green flags are signs that indicate when meeting a new person whether a good relationship can develop from it....

Review Samsung SSD 990 PRO PCIe 4.0: ultimate SSD

Samsung offers a device for practically every user. Read in this review for whom the new Samsung SSD 990 PRO is intended, what...

Nissan Ariya – AutoWeek Test

How good is the electric Nissan Ariya?The electric Nissan Ariya is the long-awaited follow-up to the Leaf, which was actually the world's first versatile...

Related Stories

Stay on op - Ge the daily news in your inbox