A boy kicks a football from ground level with a certain initial velocity at an angle 30.0° above the horizontal. In 2.00 seconds the ball completes its trajectory and hits the ground. What is the initial velocity of the ball?
A) 9.80 m/s
B) 4.90 m/s
C) 39.2 m/s
D) 19.6 m/s
E) 78.4 m/s

Question

Quizplus · Accepted Answer

We can use the kinematic equation:
y = viy*t + (1/2)at^2
where y = 0 (since the ball returns to the ground level), viy is the initial vertical velocity (which can be calculated using the initial velocity and the angle), a is the acceleration due to gravity (-9.8 m/s^2), and t is the time of flight (which is given as 2.00 seconds).

Substituting the values, we get:
0 = vi*sin(30°)*2.00 + (1/2)*(-9.8)*(2.00)^2

Solving for vi, we get:
vi = 19.6 m/s

Therefore, the answer is D: 19.6 m/s.

A Boy Kicks a Football from Ground Level with a Certain