# Newton's Second Law of Motion (problems)

1) A 1.08 x 10^3 kg car uniformly accelerates for 12.0s from rest.. During this time the car travels 132 m north. What is the net force acting on the car during this acceleration?

2) A 1.20 x 10^3 kg car accelerates uniformly from 5.0m/s east to 12m/s east. During this acceleration the car travels 94m. What is the net force acting on the car during this acceleration?

I have no idea how my teacher got the answer 1.98 x 10^3 N north for Question 1 and 7.6 x 10^2 N east for question 2. Can anyone help me???

1) First $$F = ma$$, also you know the distance and time and that it started from rest, you can find the acceleration easily using $$d=\frac{at^2}{2}$$.

2) I am guessing you are having problems finding the acceleration. The acceleration is uniform here, so use $$d=\frac{v_1-v_0}{2}t$$ to find the time it takes to travel ($$v_0$$ and $$v_1$$ are the inital and final velocities respectively) and then using that time $$d=\frac{at^2}{2}+v_0t$$.

I hope this helps. Do not be discouraged when you cannot solve these, I almost failed physics my freshman year.

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ok.. i got number 1 but i'm basically stuck on number 2. can u explain it clearly please?

In order to calculate the net force, you need the mass (given) and the acceleration. You will also indicate a direction of the force for this problem, as force is a vector quantity.

So, we all know $$F_{net} = ma$$

You have the mass, so let's solve for the acceleration.

Use one of those nice kinematic equations... I'll pick one.

$$v_{f}^2 = v_{i}^2 + 2ad$$

You know everything but "a", so use those algebra skills and solve for it.

HallsofIvy