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# If a ball is dropped, how long must it fall to attain a velocity of 12.55m/s?

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If a ball is dropped, how long must it fall to attain a velocity of 12.55m/s?

Guest Mar 22, 2015

#3
+92219
+10

I shall show you the calculus solution

$$\\\ddot{y}=9.8\\\\ \dot{y}=9.8t+c\\\\ when \;\;t=0\;\;\dot{y}=0\;\;so\;\;c=0\\\\ \dot{y}=9.8t\\\\ Find t when \;\dot{y}=12.55\\\\ 12.55=9.8t\\\\ t=\frac{12.55}{9.8}=1.28sec$$

There you go - that was pretty simple too.  :)

Melody  Mar 23, 2015
Sort:

#1
+92219
+10

did you need to use physics formula or calculus?

If a ball is dropped, how long must it fall to attain a velocity of 12.55m/s?

I will assume that you are on Earth near seal level      gravity=9.8m/s^2

a=9.8,   u=0,   v=12.55,   t=?

v=u+at

12.55=0+9.8*t

12.55=9.8t

$${\frac{{\mathtt{12.55}}}{{\mathtt{9.8}}}} = {\frac{{\mathtt{251}}}{{\mathtt{196}}}} = {\mathtt{1.280\: \!612\: \!244\: \!897\: \!959\: \!2}}$$

1.28 seconds

If you need to use calc you can ask and it shall be done.

Melody  Mar 23, 2015
#2
+85759
+5

That linear formula looks pretty straight forward to me, Melody......

Is it more confusing with calculus???

CPhill  Mar 23, 2015
#3
+92219
+10

I shall show you the calculus solution

$$\\\ddot{y}=9.8\\\\ \dot{y}=9.8t+c\\\\ when \;\;t=0\;\;\dot{y}=0\;\;so\;\;c=0\\\\ \dot{y}=9.8t\\\\ Find t when \;\dot{y}=12.55\\\\ 12.55=9.8t\\\\ t=\frac{12.55}{9.8}=1.28sec$$

There you go - that was pretty simple too.  :)

Melody  Mar 23, 2015
#4
+85759
0

Yep...equally easy......

CPhill  Mar 23, 2015

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