A father demonstrates projectile motion to his children by placing a pea on his fork's handle and rapidly depressing the curved tines, launching the pea to heights above the dining room table. Suppose the pea is launched at 7.47 m/s at an angle of 81.0° above the table. With what speed (in m/s) does the pea strike the ceiling 2.10 m above the table?

Respuesta :

Given

Initial velocity is u=7.47 m/s

The angle is

[tex]\theta=81^0[/tex]

The vertical height travelled, h=2.10 m

To find

The final speed of the pea.

Explanation

Along the vertical direction,

The final speed is given by the equation of kinematic

[tex]v_y^2=u_y^2+2ah[/tex]

Putting the values

[tex]\begin{gathered} v_y^2=(7.47sin81^o)^2+2(-9.81)\times2.1 \\ \Rightarrow v_y=3.63\text{ m/s} \end{gathered}[/tex]

Along the horizontal direction,

the speed is constant throughout the projectile

Thus,

[tex]v_x=7.47cos81^0=1.168\text{ m/s}[/tex]

So the final velocity of the pea is

[tex]\begin{gathered} v=\sqrt{(3.63)^2+(1.168)^2} \\ \Rightarrow v=3.81\text{ m/s} \end{gathered}[/tex]

Conclusion

The final velocity is 3.81 m/s