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[Use g = 10 m/s2, use the values of sine, cosine, and tangent found on the AP Physics Table of Information.]On a long, level playfield, a player kicks a football with an initial speed of 20 m/s at an angle of 53° from the ground.(a) At what time does the ball reach its highest point?____ s(b) What is greatest height reached by the ball during projectile motion?____ m

Sagot :

(a) In order to determine the time at which the ball reaches its maximum height, use the following formula:

[tex]v_y=v_{oy}-gt[/tex]

where,

vy: final speed at the maximum height = 0m/s

voy: vertical component of the initial velocity

g: gravitational acceleration constant = 9.8m/s^2

t: time

The vertical component of the initial velocity is:

[tex]v_{oy}=v_o\sin (53)=(\frac{20m}{s})(\sin (53))=\frac{15.97m}{s}[/tex]

Solve the equation for t and replace the values of the rest of the parameters:

[tex]t=\frac{v_{oy}-v_y}{g}=\frac{\frac{15.97m}{s}-\frac{0m}{s}}{\frac{9.8m}{s^2}}=1.63s[/tex]

Hence, after 1.63s the ball has reached its maximum height.

(ii) Use the following formula to determine the greatest height:

[tex]y_{\max }=\frac{v^2_{oy}}{2g}=\frac{(\frac{15.97m}{s})^2}{2\cdot\frac{9.8m}{s^2}}=13.01m[/tex]

Hence, the maximum height is approximately 13.01m