Two dimensional motion problem (kicking a soccer ball into the goal)

  • #1
Ineedhelpwithphysics
42
7
Homework Statement
Carli Lloyd scored half-field goal (53 m) vs. Japan with a beautiful projectile motion. It looks from the video that the ball was inthe air for 2.0 seconds. What was the angle of the ball when it left her foot?
Relevant Equations
VoX = vcos(theta)
VoY = vsin(theta)
Vf(y) = Vo(y) + a(y)t
Delta y = VoY + 1/2a(y)t^2
I did this too fast idk if I'm wrong

So for the x component
use the formula d = rt / delta x = v*t
26 = vcos(theta)

y component
use the displacement formula
19.6 = vsin(theta)

tan^-1(19.6/26) = 36.5 degrees
the answer key says 20.2 degrees idk whats wrong
 
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  • #2
I did wrong calculations please ignore this
 
  • #3
I get the angle 20.67 with ##g=10m/s^2##.
Your first equation is almost correct, it should be $$\frac{53}{2}=v_0\cos\theta$$
But no clue how did you infer the 2nd equation.
Hint: if the total flight time is 2.0 sec what is the total ascent time, ##t_A## ,that is the time the ball rises from the initial point to its highest point, and how ##v_{0y}=v_0\sin\theta## relates to ##t_A##?

Now I see that your second equation is also almost..... correct up to a factor of 2 e hehe and with ##g=9.8m/s^2##
 
  • #4
What is the formula the for range ##R## of a projectile and its total time of flight ##T##? Those two are the ones you need to answer the question @Ineedhelpwithphysics
 

Related to Two dimensional motion problem (kicking a soccer ball into the goal)

1. How does the angle of the kick affect the trajectory of the soccer ball?

The angle of the kick determines the initial direction of the ball's motion. A higher angle will result in a higher trajectory, while a lower angle will result in a lower trajectory. The optimal angle for kicking a soccer ball into the goal is typically around 45 degrees.

2. What factors affect the distance the ball travels after being kicked?

The distance the ball travels after being kicked is affected by the initial velocity of the kick, the angle of the kick, air resistance, and the surface on which the ball is kicked. A stronger kick with a higher angle will result in the ball traveling further.

3. How does air resistance impact the motion of the soccer ball?

Air resistance slows down the motion of the soccer ball by exerting a force opposite to the direction of motion. This force increases with the speed of the ball and the surface area exposed to the air. Therefore, a soccer ball will travel a shorter distance in the presence of air resistance.

4. How does the height of the goal affect the trajectory of the ball?

The height of the goal affects the trajectory of the ball by providing a target for the kick. A higher goal will require a higher trajectory to clear it, while a lower goal will require a lower trajectory. The height of the goal influences the angle at which the ball needs to be kicked.

5. What is the optimal speed for kicking a soccer ball into the goal?

The optimal speed for kicking a soccer ball into the goal depends on the distance to the goal, the angle of the kick, and air resistance. Generally, a moderate speed that allows the ball to reach the goal before losing too much speed to air resistance is ideal for accuracy and distance.

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