Question

A soccer player attempting to steal the ball from an opponent was extending her knee at 50 deg/s when her foot struck the opponent's shin pads. If the player's knee was stopped (0 deg/s) within 0.2 seconds, what angular acceleration did the knee experience?

Answer 1

`\alpha = -4.36 rad/s^2`

Step-by-step explanation:

Initial angular speed of the player is given as

`\omega = 50 deg/s`

here we know that

`1 deg = (\pi)/(180) rad`

now we know that

`\omega = 50(\pi)/(180)`

`\omega = 0.87 rad/s`

now its speed comes to zero in 0.2 s

so angular acceleration is given as

`\alpha = (\omega_f - \omega_i)/(\Delta t)`

`\alpha = (0 - 0.87 rad/s)/(0.2 s)`

`\alpha = -4.36 rad/s^2`