1. ## Physics Help

A migrating bird is initially flying south at 7 m/s. To avoid hitting a high-rise building, the bird veers and changes its velocity to 6 m/s east over a period of 2 s. What is the bird's average acceleration (magnitude and direction) during this 2 s interval?

2. ## Re: Physics Help

Originally Posted by Louisana1
A migrating bird is initially flying south at 7 m/s. To avoid hitting a high-rise building, the bird veers and changes its velocity to 6 m/s east over a period of 2 s. What is the bird's average acceleration (magnitude and direction) during this 2 s interval?
Hi Louisana1!

Can you write the initial velocity as a vector?
And the final velocity as a vector as well?

If so, can you fill them in the formula for average accelation?
That formula is:
$\displaystyle \vec a_{average} = {1 \over \Delta t} (\vec v_{final} - \vec v_{initial})$

-1/2

4. ## Re: Physics Help

subtracting vectors ...

$\displaystyle i$ = unit vector in positive x-direction (East)

$\displaystyle j$ = unit vector in positive y-direction (North)

$\displaystyle v_0 = -7j$

$\displaystyle v_f = 6i$

$\displaystyle \Delta v = v_f - v_0 = 6i + 7j$

$\displaystyle a = \frac{\Delta v}{\Delta t} = \frac{6i + 7j}{2} = 3i +3.5j$

$\displaystyle |a| = \sqrt{3^2 + 3.5^2} = 4.6 \, m/s^2$

direction of the average acceleration vector ...

$\displaystyle \theta = \arctan\left(\frac{3.5}{3}\right) = 49^\circ$

5. ## Re: Physics Help

not sure how you got the 49
Thanks skeeter

6. ## Re: Physics Help

the inverse tangent function on my calculator ...

7. ## Re: Physics Help

It said it was wrong on my online homework

8. ## Re: Physics Help

Originally Posted by Louisana1
It said it was wrong on my online homework
the angle is rounded to the nearest degree ... what is the criteria for entering answers as far as decimal places? If it's significant figures, it should be 50 degrees.

9. ## Re: Physics Help

still wrong I'm trying to figure it out too

10. ## Re: Physics Help

What was wrong? What answer did you give?

11. ## Re: Physics Help

the 49 degrees is incorrect the other part is right