Year 11 motion/vector problem?

[caitie_72]

Homework Statement

I'm really not good at motion. It just doesn't seem to come easily to me, which is kind of disapointing, because physics is my favourite subject.

Question: A body of mass 5kg is moving in a north easterly direction with a velocity of 28.3 m/s. If a westerly wind acts on it with a force of 73.5N what is the change in momentum after 8s.

Homework Equations

F = ma, a = v/s
?

The Attempt at a Solution

I figured i'd find the velocity of the force.
F = ma
73.5 = 5a
a= 14.7

a = v/t
v = 14.7 * 8
v = 117.6

difference in p = m(v-u)
p = 5(117.6-28.3)

But this doesn't give the right answer. The answer is 588 N s East.

I know i probably need to draw vectors and what not but the whole concept of vectors confuses me deeply. :(
Could you explain to me how the diagram would work? Would i need to use non-right trig? And also, what am i doing wrong?
I don't understand a lot of the concepts of vectors and motion, so try and explain it in the simplest way possible, because I am not great at this stuff.

Any help is appreciated. Thanks :)

 

[Redbelly98]

You need to think about velocity components for this one.

The change in velocity is in the east/west direction. So what was the initial east/west velocity component?

p.s. welcome to PF.

 

[thomate1]

Hello,

First of all, it's great that you are seeking help and trying to understand the concepts of motion and vectors. These are important topics in physics and it's important to have a good grasp on them.

To start, let's define a few things:

- Momentum: Momentum is the product of an object's mass and its velocity. It is a vector quantity, meaning it has both magnitude and direction. In this problem, the momentum of the body is given by p = mv, where m is the mass (5kg) and v is the velocity (28.3 m/s).

- Force: Force is a vector quantity that causes a change in an object's state of motion. In this problem, the force acting on the body is given by F = 73.5N.

Now, let's break down the problem step by step:

1. First, we need to find the change in momentum after 8 seconds. This can be calculated using the formula p = m(v-u), where m is the mass (5kg), v is the final velocity and u is the initial velocity.

2. We are given the initial velocity of the body, which is 28.3 m/s in the north-easterly direction. To find the final velocity, we need to take into account the force acting on the body.

3. Since the force is acting in the westerly direction, it will cause a change in the body's velocity in that direction. To find the final velocity, we can use the equation F = ma, where a is the acceleration caused by the force.

4. We can rearrange this equation to get a = F/m. Plugging in the values, we get a = 73.5/5 = 14.7 m/s^2. This is the acceleration caused by the force.

5. Now, we can use the equation v = u + at to find the final velocity. Plugging in the values, we get v = 28.3 + (14.7*8) = 28.3 + 117.6 = 145.9 m/s.

6. Now, we have the final velocity, v = 145.9 m/s, and the initial velocity, u = 28.3 m/s. Plugging these values in the formula p = m(v-u), we get p = 5(145.9-28.3) = 588 N