Not sure where to start for number 4 and 5. I think I got the first part of 4 right but unsure!! Any help is greatly appreciated!!!

Question

anonymous · Answer

5. A 39,250 N force is applied to a 7200kg car initially at rest .  what is the acceleration rate? How fast will the car be moving after 3,8 seconds? Sorry if you couldn't see the picture.

ganeshie8 · Answer

use newton's second law $F=ma$

anonymous · Answer

39,250 =7200 *a 39,250/7200 =a=5.5 m/s

ganeshie8 · Answer

careful about the units

a=5.5 m/s^2

anonymous · Answer

ok. How do I calculate how fast it's going to be after 3.8 seconds. Do I use v=10 * t but that has something to od with free fall? So, no?

ganeshie8 · Answer

so the car is being accelerated for 3.8 seconds

ganeshie8 · Answer

$a = 5.5$
$t=3.8$
initial velocity, $u=0$

final velocity, $v=?$

anonymous · Answer

5.58 * 3.8 =20.9 m/s

ganeshie8 · Answer

right, but it seems you have a rounding error.. 
maybe just enter below into the calculator :

39250/7200*3.8 = 20.7 m/s

anonymous · Answer

ok . I think I understand. Thank you so much!!!!

ganeshie8 · Answer

yw!

ganeshie8 · Answer

as you can see, "change in speed" requires acceleration

no acceleration means no "change in speed"