A high-speed dart is shot from ground level with a speed of 150 m/s at an angle 30° above the horizontal.What is the vertical component of its velocity after 4.0 s if air resistance is neglected?
A)150 m/s
B)36 m/s
C)130 m/s
D)75 m/s
E)38 m/s

Question

Quizplus · Accepted Answer

The vertical component of velocity can be found using the formula v_y = v*sin(theta), where v is the initial velocity and theta is the angle above the horizontal. 
v_y = 150*sin(30) = 75 m/s (upward) 
After 4 seconds, the vertical velocity will decrease due to gravity: 
v_y = v_y0 - gt 
v_y = 75 - 9.8*4 = 36 m/s (upward) 
Therefore, the best choice is B.

A High-Speed Dart Is Shot from Ground Level with a Speed