Question

an object is thrown horizontally from a point A from a tower and hits the ground 3 second later at B the line from A to B makes an angle 30 degree with the horizontal. the initial velocity of the object is:( taken g = 10 M per second)

Answer 1

Average velocity is defined to be the change in position divided by the time of travel.

The object takes 3 sec to fall,

                                      $AC=h=\frac {1} {2} gt^2\\= \frac {1} {2} \times 10 \times 9=45 m$

                                      tan 30° $= AC/BC = 1/ \sqrt{3}$

                                      $BC=\sqrt{3}AC=45\sqrt{3}m$

So,  Initial velocity  = BC/3  

                                     Initial velocity = $15\sqrt{3} m/sec$

Answer 2

Answer:

Explanation:

Object takes 3s to fall.

Hence AC = height =  

2

1

​  

gt  

2

=  

2

1

​  

×10×9=45m

Also:

tan30  

∘

=  

BC

AC

​  

=  

3

​  

 

1

​  

 

BC=  

3

​  

AC=45  

3

​  

m

The object covers AB in 3s, hence initial velocity =  

3

BC

​  

=15  

3

​  

ms  

−