Solving Forces and Acceleration Problems in Physics - Study Group Help

Newtons at 8.8 degrees to the right of forward directionIn summary, the conversation involves a high school student seeking help with a physics problem involving two forces acting on a car. The student has attempted to solve the problem using trigonometry, but is struggling to find the correct answer. An expert advises the student to use component form and a coordinate system to find the resultant force, and then use Pythagoras and arctan to find the magnitude and angle of the force. The student is still struggling to get the correct answer and seeks further help.
  • #1
caity232
Hello, I am a junior in High School and some of my friends in my physics class and I have a study group for our weekly bookwork that our teacher assigns. We have tried all week to figure out this one problem but to no avail. The problem is as follows:
Two forces are applied to a car in an effort to move it. A)What is the resultant of these two forces? B) If
the car has a mass of 3000 Kg, what acceleration does
it have?

the diagram of the car shows that it is being pulled
in two different directions one arrow is pointing
northeast with a force of 400 Newtons at an angle of
30 degrees, and the other direction is northwest at an angle
of 10 degrees and a force of 450 Newtons.

I tried using 400cos30 and 450cos10, but it doesn't work. The answers are in the back of the book, but I'm looking for how to do the math and I don't want to just copy the answers down because I would like to know how to solve this. If it helps, the answers are:
A) 789 Newtons at 8.8 degrees to the right of forward direction
B) 0.266 m/s^2 in direcrion of resultant force
Thank you in advance, and please help me with the math in this problem.
 
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  • #2
I tried using 400cos30 and 450cos10, but it doesn't work.
Close, very close.

You have to remember that acceleration is also a vector, and so also need to be seen in terms of components.

So, what you want to do is first to define a coordinate system. Put North as y, say, and East as x.

Then, you 400cos30, 400sin30 and so on to put to two forces in component form along the two directions, and then sum the x components and sum the y components. Now you have the resultant force in component form.

From the presentation of the answer, you need then to calculate the angle and magnitude of this force. For that use pythagoras and arctan.

For acceleration, it's an easy matter of using f=ma on the magnitude.
 
  • #3
when you add the x and y components you get 1067.71 ... when i did 400cos30 and 400sin30 i got 546.41 and when i did 450cos10 and 450sin10 i got 1067.71... The answer in the back of the book in 789? Can I have some further help with this?
 
  • #4
Why are you adding the x and y components? The length of a vector is not the length of its components. Once you have found the components and add "x to x" and "y to y" to find the resultant, you can use "Pythagorean Theorem" to find the length.
 
  • #5
it still doesn't give you 789
 

1. How do I calculate the net force on an object?

To calculate the net force on an object, you need to add up all the individual forces acting on the object. This can be done by using vector addition, where you take into account the magnitudes and directions of each force.

2. What is the relationship between force and acceleration?

According to Newton's second law of motion, the force applied to an object is directly proportional to its acceleration. This means that the greater the force, the greater the acceleration, and vice versa.

3. How do I solve for acceleration in a physics problem?

To solve for acceleration, you can use the equation a = F/m, where a is the acceleration, F is the net force, and m is the mass of the object. You can also rearrange this equation to solve for other variables, such as mass or force.

4. What are some common mistakes to avoid when solving forces and acceleration problems?

One common mistake is forgetting to take into account the direction of the forces. Another is using incorrect units or not converting units properly. It is also important to double-check your calculations and to make sure you are using the correct formulas.

5. How can a study group help me with solving forces and acceleration problems?

A study group can provide a supportive and collaborative environment where you can discuss and work through problems together. Sharing different perspectives and approaches can also help you better understand the concepts and improve your problem-solving skills.

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