A force in the negative direction of an x axis is applied for 34 ms to a 0.40 kg ball initially moving at 16 m/s in the positive direction of the axis. The force varies in magnitude, and the impulse has magnitude 32.4 N·s.(a) What is the ball's speed just after the force is applied?____m/s(b) What is the average magnitude of the force?___N

Respuesta :

(a) 96 m/s

The impulse theorem states that the impulse exerted on the ball is equal to the change in momentum of the ball:

[tex]I=\Delta p=m \Delta v = m(v-u)[/tex]

where

[tex]I=32.4 Ns[/tex] is the impulse exerted on the ball

[tex]m=0.40 kg[/tex] is the mass of the ball

[tex]v[/tex] is the final speed of the ball

[tex]u=16 m/s[/tex] is the initial speed of the ball

Solving the equation for v, we find

[tex]v=\frac{I}{m}+u=\frac{32.4 Ns}{0.40 kg}+16 m/s=96 m/s[/tex]

(b) 952.9 N

The impulse is also equal to the product between the average force and the contact time:

[tex]I=F\Delta t[/tex]

where here we have

[tex]I=32.4 Ns[/tex] is the impulse

[tex]F[/tex] is the average force

[tex]\Delta t=34 ms=0.034 s[/tex] is the contact time

Solving the equation for F, we find the force:

[tex]F=\frac{I}{\Delta t}=\frac{32.4 Ns}{0.034 s}=952.9 N[/tex]