What is the Magnitude of Displacement for Various Directions and Distances?

In summary, the conversation is about solving problems involving displacement using the equations R^2=a^2 + b^2 and R^2= a^2 + b^2 - 2ab COS(angle). The first equation is used to find the magnitude of displacement in a straight line, while the second equation is used when there is a change in direction. The fourth problem is a bit confusing and the person is unsure of how to solve it, but they could potentially use both equations to find the resultant magnitude. The conversation ends with the person expressing their struggle with the subject and their recent low grades.
  • #1
star227
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Okay i don't have the best physics teacher :-/ he often gets confused with what he's teaching and shows us the wrong thing...We have four problems for homework and I would just like one of you experts to check over it ;)

1. A car is driven 125 km due west, then 65 km due south. What is the magnitude of displacement? R^2=a^2 + b^2
R^2=125^2 + 65^2
R^2=19850
R=140.9 (about)
2. A shopper walks from the door of the mall to her car 250m down a lnae of cars, then turns 90 degrees to the right and walks an additional 60m. What is the magnitude of the displacement of her car from the mall door?
R^2=a^2 + b^2
R^2=60^2 + 250^2
R^2=66100
R=257.1 (about)
3. A hiker walks 4.5 km in one direction, then makes a 45 degree turn to the right and walks another 6.4 km. What is the magnitude of her displacement?
R^2= a^2 + b^2 - 2ab COS(angle)
R^2= 4.5^2 + 6.4 ^2 -2(4.5)(6.4)cos45
R^2=20.25 + 40.96- 40.729
R^2=20.481
R=4.526 (about)
4. What is the magnitude of your displacement when you follow directions that tell you to walk 225 m in one direction, make a 90 degree turn to the left and walk 350 m, then make a 30 degree turn to the right and walk 125 m?
I'm not sure how to go about doing this one but what I DO know is
how the triangle looks and the angle measurements. I'm just not
sure what it is I'm supposed to be writing down. A hand please lol?
 
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  • #2
...would I use the first or second equation? What about a combination of both? ...maybe its a trick question lol maybe its right there you just have to know what it is...
 
  • #3
You could use both. Get the resultant magnitude (R1) from the first two directions. And then find the resultant (R2) from R1 and the 3rd vector.
 
  • #4
thanks! is the rest of it right?
 
  • #5
isnt the resultant vector 125? whoaaa...*confused*
 
  • #6
To find the resultant magnitude I would use r2=a2+b2 rite? i don't know what youre talking about the next part that confuses me..3rd vector is 125 correct?
 
  • #7
please someone help my gpa is plummeting thru tha ground I've made 2 awful homework grades recently: 71% and a 76%! :'(
 

What is the definition of magnitude of displacement?

Magnitude of displacement is the distance and direction from the starting point to the ending point of an object's motion.

What is the difference between displacement and distance?

Displacement refers to the shortest distance between the starting and ending point, while distance refers to the total length traveled by an object.

What unit is used to measure magnitude of displacement?

Magnitude of displacement is typically measured in units of length such as meters, kilometers, or miles.

Can magnitude of displacement be negative?

Yes, magnitude of displacement can be negative if the ending point is located behind the starting point. This indicates that the object has moved in the opposite direction of its initial motion.

How is magnitude of displacement calculated?

Magnitude of displacement can be calculated using the Pythagorean theorem, where the magnitude is equal to the square root of the sum of the squares of the distance traveled in each direction.

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