# Vector and acceleration problem

1. Sep 23, 2007

### Zeitgeist

1. The problem statement, all variables and given/known data
A bird takes 8.5s to fly from position A{ V = 4.4 m/s [31° S of E]} to position B{ v = 7.8 m/s [25° N of E]}. Determine the average acceleration.

2. Relevant equations
$$a_{ave} = \Delta V / \Delta t$$
$$\Delta Vx = Vbx + (-Vax)$$
$$\Delta Vy = Vby + (-Vay)$$

3. The attempt at a solution
$$\Delta Vx = Vbx + (-Vax)$$
= $$Vb \sin \Theta + (-Va \cos \beta)$$
= $$7.8 m/s (\sin31) - 4.4 m/s(\cos25)$$
= 0.0295 m/s

$$\Delta Vy = Vby + (-Vax)$$
= $$Vb \cos \Theta + (-Va \sin \beta)$$
= $$7.8 m/s (\cos31) + 4.4 m/s (\sin25)$$
= 8.545 m/s

$$\mid \Delta V\mid^2 = \mid \Delta Vx \mid^2 + \mid \Delta Vy \mid^2$$
= $$(0.0295)^2 + (8.545)^2$$
= 8.545 m/s

$$a_{ave} = \Delta V / \Delta t$$
= (8.545m/s) / (8.5s)
= 1.005

This is how far i've got and I checked the answer with my textbook it says that the answer should be 0.76 m/s ^2.

Can someone help please?

Last edited: Sep 23, 2007