question_answer

A body starts moving with a velocity of 6 m/s making an angle of\[30{}^\circ \]with the x-axis. It has a uniform acceleration of\[3\text{ }m/{{s}^{2}}\]in the direction of\[x-\]axis. After 5 seconds, the ^-component of its velocity will be, in m/s.

A)  \[3\sqrt{{}}3\]               

B)  15

C)  18    

D)  21

Correct Answer: C

Solution :

  Along y-axis  Initial velocity \[=v\,cos60{}^\circ \] \[=6\,cos60{}^\circ =\frac{6}{2}=3\] Acceleration\[(a)=3\text{ }m/{{s}^{2}}\] Time\[(t)=5s\] \[\therefore \]Final velocity\[=V\] \[V=u+at=(3+3\times 5)=18\text{ }m/s\].