Respuesta :
Answer:
Explanation:
Given
Firemen shoot the water stream at an angle of \alpha
launch speed [tex]u=25\ m/s[/tex]
it takes it [tex]t=3\ s[/tex] to reach the building
Building is [tex]R=45\ m[/tex] from launch point
Considering horizontal motion
[tex]R=u\cos \alpha \cdot t[/tex]
[tex]45=25\cos \alpha \cdot 3[/tex]
[tex]\cos \alpha =0.6[/tex]
[tex]\alpha =53.13^{\circ}[/tex]
(b)At highest point vertical velocity becomes zero and there is only horizontal velocity
[tex]velocity=u\cos \alpha [/tex]
[tex]velocity=25\cdot \cos \53.13[/tex]
[tex]velocity=15\ m/s[/tex]
net acceleration will be acceleration due to gravity which will be acting downward
(c)height reached by water stream is given by
[tex]y=ut+\frac{1}{2}at^2[/tex]
where,
y=displacement
u=initial velocity in vertical direction
a=acceleration
t=time
net velocity at this instant is the vector sum of vertical and horizontal velocity
vertical velocity [tex]v_y=u\sin \alpha -g\cdot t[/tex]
[tex]v_y=25\sin (53.13)-9.8\cdot 3[/tex]
[tex]v_y=-9.4\ m/s[/tex]
Horizontal velocity [tex]v_x=u\cos \alpha =25\cos (53.13)[/tex]
[tex]v_x=15[/tex]
net velocity [tex]v_{net}=\sqrt{(v_x)^2+(v_y)^2}[/tex]
[tex]v_{net}=\sqrt{313.36}=17.70\ m/s[/tex]
