Newton's Laws grade 11 physics

In summary, 45N is the sum of two perpendicular forces, x and y, and the resultant force is 0.4m/s^2.
  • #1
anna sung
46
0

Homework Statement


A toboggan with a mass of 15kg is being pulled with an applied force of 45 N at an angle of 40degrees to the horizontal. What is the acclecration if the force of friction opposing the motion is 28 N?

Homework Equations



Is this question related to the x and y component rules?
I tried finding the x and y of 45 N and 28N. I don't understand how my answer is not even close to the answer in the book.

The Attempt at a Solution


45N (E40degreeN)
x-component:
45(cos40)=34.37N
y-component:
45(sin40)=28.9N

28N (W40degreeS)
x-component:
28(cos40)=-21.4N
28(sin40)=-18N

X-components
34.37-21.4= 13.07N
Y-components
28.9-18=10.92N
[tex]\sqrt{13.07^2+10.92^2}[/tex]
= 17N
Fun=ma
a=Fun/m
a=17N/15kg
a=1.1m/s^2

The answer in the book is 0.4m/s^2
sorry about this mess. its my first time posting a question.
 
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  • #2
Your error was inpropper diagram, in this kind of physics the 3 basic rules are draw draw draw.


28N <--- ______) ----> 45Cos(40)

this is a representation of the horizontal component forces acting on the toboggan (the sled).

subtracting them you should get approx:

6.47N the right direction of the screen

therefore then applying F=ma

a = F / m

a = 6.47 / 15

a = 0.431 m/s/s QED =D

Hope this helps mate


anna sung said:

Homework Statement


A toboggan with a mass of 15kg is being pulled with an applied force of 45 N at an angle of 40degrees to the horizontal. What is the acclecration if the force of friction opposing the motion is 28 N?


Homework Equations



Is this question related to the x and y component rules?
I tried finding the x and y of 45 N and 28N. I don't understand how my answer is not even close to the answer in the book.

The Attempt at a Solution


45N (E40degreeN)
x-component:
45(cos40)=34.37N
y-component:
45(sin40)=28.9N

28N (W40degreeS)
x-component:
28(cos40)=-21.4N
28(sin40)=-18N

X-components
34.37-21.4= 13.07N
Y-components
28.9-18=10.92N
[tex]\sqrt{13.07^2+10.92^2}[/tex]
= 17N
Fun=ma
a=Fun/m
a=17N/15kg
a=1.1m/s^2

The answer in the book is 0.4m/s^2
sorry about this mess. its my first time posting a question.
 
  • #3
oh thanks i get it. but I am still not sure why 45cos40
why do we need to get the x component what does this number represent?
 
  • #4
Hello again,

well we are considering only the x component because the motion of the sled is in the horizontal plane, the x plane.

this number the 45cos 40 represents the force, the component force present in the x axis. Basic maths; pythagoras theorem you were right to apply it.

The principle behind this is that the hypotenuse squared is the sum of the x component squared and the y component squared. In this case your hypotenuse is the 45N given.

If you adopt vectors from mathematics you will see why later on, but for this question you have understand that the force to the right is not 45N but a component of that the 45cos 40 which is less than the 45N (because some of that is going to the force in the y direction as well).

In simple terms that 45N stems from two forces which are perpendicular to each other; x and y.

Hope this answers your question =)
 
  • #5
haha you're welcome, sorry for confusing you ... I tried my best to describe it but if we had some sort of visual aid I'm sure you would have understood it very well.

If you need anything please feel free to email me or send me a private message. I will do my best =)

All the best with your studies, I assure you physics is an endlessly facinating subject.
 

1. What are Newton's Laws of Motion?

Newton's Laws of Motion are three fundamental principles that describe the motion of objects in the universe. They were developed by Sir Isaac Newton in the 17th century and are still used today to understand the behavior of objects in motion.

2. What is the first law of motion?

The first law of motion, also known as the law of inertia, states that an object at rest will remain at rest and an object in motion will remain in motion at a constant velocity unless acted upon by an external force. In other words, objects tend to resist changes in their motion.

3. What is the second law of motion?

The second law of motion states that the acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to its mass. This means that the larger the force applied to an object, the greater its acceleration will be. Similarly, the more massive an object is, the less it will accelerate for a given force.

4. What is the third law of motion?

The third law of motion, also known as the law of action and reaction, states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object will exert an equal and opposite force back on the first object. Forces always occur in pairs.

5. How do Newton's Laws of Motion relate to everyday life?

Newton's Laws of Motion can be observed in many everyday situations. For example, the first law can explain why objects on a table won't move unless a force is applied to them, and the second law can explain why it takes more force to push a heavy object than a light one. The third law can be seen in actions such as walking, where the force of your foot pushing against the ground is met with an equal and opposite force from the ground pushing back on your foot.

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