A0.42kgSoccerBallIsMovingW/AVelocityOf12m/sDownfield.APlayerKicksBallSoThatItHasAFinalVelocityOf18m/sDownfield.

Question

What impulse, or change in momentum, did the ball experience?

Also, find the constant force exerted by the player's foot on the ball if the two are in contact for 0.020s 

Answer 1

A0.42kgSoccerBallIsMovingW/AVelocityOf12m/sDownfield.APlayerKicksBallSoThatItHasAFinalVelocityOf18m/sDownfield.

 

Impulse Momentum Theorem states that the impulse given to an object will produce a change in momentum equal in size to the impulse.

The Impulse/Change in momentum equation is: F • t = Δp, where F is the force applied, t is the period of time the force is applied to the object and Δp is the change in momentum. The change in momentum can also be written as: (m • Δv), where m is the mass of the object and Δv is the change in velocity. The change in velocity can also be written as: (v_f - v_i), where v_f is the final velocity and v_i is the initial velocity. In other words, the velocities before and after the force is applied.

GIVEN:

m = 0.42kg

v_i = 12 m/s

v_f = 18 m/s, assuming that downfield means the ball was kicked in the same direction it was moving.

t = 0.020s

F • t = m(v_f - v_i)

UNKNOWN:

F = ? 

 

SOLUTION:

F(0.020 s) = 0.42 kg(18 m/s - 12 m/s)

 

F(0.020 s) = 2.52 kg•m/s

 

F = (2.52 kg•m/s) / (0.020 s)

 

F = 126 kg•m/s/s or 126 kg•m/s² or 126 N (Newton's)