Calculating Force of Bat on Ball: Physics Homework Solution

[futureteacher]

Homework Statement

A 0.145 ball is pitched at 37 m/s and is hit on a horizontal line drive at 51.5 m/s. If the contact time between the ball and the bat is 3.5x10^-3 seconds what is the avg force between the bat and the ball during contact.

Homework Equations

P=mv
$$\Sigma$$F=$$\Delta$$P/$$\Delta$$T

m_final*v_final-m_initial*v_initial/$$\Delta$$Time

factor out m (mass)
m(vfinal-vinitial)/$$\Delta$$t

The Attempt at a Solution

0.145kg(51.5m/s-37.0m/s)/(3.5*10^-3)

i get 600N but my webwork says that not right i have no idea what I am doing wrong

 

[Andrew Mason]

Homework Statement

A 0.145 ball is pitched at 37 m/s and is hit on a horizontal line drive at 51.5 m/s. If the contact time between the ball and the bat is 3.5x10^-3 seconds what is the avg force between the bat and the ball during contact.

Homework Equations

P=mv
$$\Sigma$$F=$$\Delta$$P/$$\Delta$$T

m_final*v_final-m_initial*v_initial/$$\Delta$$Time

factor out m (mass)
m(vfinal-vinitial)/$$\Delta$$t

The Attempt at a Solution

0.145kg(51.5m/s-37.0m/s)/(3.5*10^-3)

i get 600N but my webwork says that not right i have no idea what I am doing wrong

The change in velocity is 51.5 + 37.0 m/s. The ball is hit in the opposite direction to the pitch.

Don't forget that force and momentum are vector quantities. The definition of force is:

$$\vec F = \sum \vec F_i = \frac{d\vec p}{dt}$$

AM