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Wagon in the figure can roll down the hill without friction. When the outpot speed (Vo) is 0 m/s and the end speed (v) is 4m/s

 

How high is the hill? 

 

[WAGON] Vo = 0m/s

                           _

                                    _      

                                                  _ 

                                                                    _           [WAGON] Vo =4m/S

 May 9, 2017
 #1
avatar+14913 
+1

Wagon in the figure can roll down the hill without friction. When the outpot speed (Vo) is 0 m/s and the end speed (v) is 4m/s

How high is the hill?

 

\(E=\frac{m}{2}(v^2-v_o^2)=mgh\)

 

\(v^2-v_0^2=2gh \)

 

\((4\frac{m}{s})^2=2\cdot 9.81\frac{m}{s^2}\cdot h\)

 

\(h=16\cdot \frac{m^2}{s^2}/2\cdot9.81\cdot\frac{m}{s^2}\) 

 

\(h=\frac{16\frac{m^2}{s^2}}{2\cdot 9.81\frac{m}{s^2}}\)

 

\(h=0.815\ m\)

 

\(The \ hill \ is \ 0.815 \ m \ high.\)

 

laugh  !

 May 9, 2017
edited by asinus  May 9, 2017
 #2
avatar+33615 
+2

Use conservation of energy:

 

potential energy at the top = m*g*h   where m is mass, g is acceleration of gravity and h is height.

 

kinetic energy at the bottom = (1/2)mv2    where v is velocity

 

Equating the two we get

 

gh = (1/2)v2    or   h = (1/2)v2/g

 

You can crunch the numbers!

 

Looks like asinus has already crunched the numbers for you!

 May 9, 2017
edited by Alan  May 9, 2017

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