Car with mass of 1500kg and thrust of 4000N

[jtwitty]

Sorry; this is like soooooooo hard

Homework Statement

A car with a mass of 1500 kg has en engine which can produce 4000N of thrust. Assume that the air resistance on the car is a constant 500N. If the car starts from rest, how fast will it be moving after 10 seconds.

Homework Equations

d=1/2at²+vit
a=f/m

The Attempt at a Solution

a = 4000 / 15000
a = .2666666666666666666666666666666666666666666666666666666666
thats about as far as i can get because that a has to be wrong?

 

[jtwitty]

heres what i just came up with

netforce = 4000 - 500 = 3500

a = 3500/1500
a = 2.4

d= 1/2a(100)
d=120m

a = vf /t
vf = 24

??

 

[Clever-Name]

First you need to determine what the NET force will be on the car. In this case you have 4000N of thrust in the positive x direction (indicate as 'right' on your free body diagram), you also have a 500N resistive force due to air drag (left).

Your net force will be 4000N-500N (3500N).

Since $F = ma$, $a = \frac{F}{m} = \frac{3500}{1500} = 2.33333$

Remember to look at the units of the values you are given. For some reason you added another 0 to your mass, which is why you got that strange value for a.

From that value of a you should be able to determine the velocity now after 10 seconds, use constant acceleration forumlae.

Edit - ninja'd.

Edit2 - One small correction to your answer. Since 3500/1500 = 2.33333333, rounding up to 2.4 is incorrect. 2.3 would be the appropriate value if significant figures aren't important for this problem. Thus your final answer would be 23m/s

 

[jtwitty]

haha )

thanks so much man :)