Calculating Work Using Dot Product: Constant Force and Particle Position

In summary, the work done on the particle can be found by taking the dot product of the force and displacement vectors. The angle between the vectors can be found using the formula above.
  • #1
PsychonautQQ
784
10

Homework Statement


A constant force of 1i - 5j -8k moves (1,-4,2) (-3,2,-1), what is the work done on the particle?


Homework Equations


Avector*Bvector=ABsinθ
?? I think?

The Attempt at a Solution


I really am quite lost... but I found the coordinates for the position vector...

(-3-1)i + (2--4j) + (-1-2)k and the magnitude of the position vector is 7.81
so the unit vector is -.512i + .768j -.384k... am I on the right track here?
 
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  • #2
PsychonautQQ said:

Homework Statement


A constant force of 1i - 5j -8k moves (1,-4,2) (-3,2,-1), what is the work done on the particle?

Homework Equations


Avector*Bvector=ABsinθ
?? I think?

The Attempt at a Solution


I really am quite lost... but I found the coordinates for the position vector...

(-3-1)i + (2--4j) + (-1-2)k and the magnitude of the position vector is 7.81
so the unit vector is -.512i + .768j -.384k... am I on the right track here?

For a constant force F, the work done is just the dot product of the force with the displacement. Use that.
 
  • #3
so the force is 1i - 5j -8k and the displacement is -4i +6j -3k? so dot product would be -4 -30 - 24 = -58?
 
  • #4
How do I find the angel between these vectors?
 
  • #5
PsychonautQQ said:
so the force is 1i - 5j -8k and the displacement is -4i +6j -3k? so dot product would be -4 -30 - 24 = -58?

Yes, if the force isn't constant you need to work harder and integrate, but if it's constant, it's that easy.
 
  • #6
PsychonautQQ said:
How do I find the angel between these vectors?

Why do you think you need the angle?
 
  • #7
If you are required, separately, to find the angle between vectors, the dot product can be defined as
[tex]\vec{u}\cdot\vec{v}= |\vec{u}||\vec{v}|cos(\theta)[/tex]

where [itex]\theta[/itex] is the angle between the vectors.
 

1. What is the dot product?

The dot product, also known as the scalar product, is a mathematical operation that takes two vectors and produces a scalar quantity. It is defined as the product of the magnitudes of the two vectors and the cosine of the angle between them.

2. How do you calculate the dot product?

The dot product can be calculated by multiplying the corresponding components of the two vectors and then summing the products. It can also be calculated using the magnitudes of the two vectors and the angle between them.

3. What is the significance of the dot product?

The dot product has several important applications in mathematics and physics. It can be used to find the angle between two vectors, determine if two vectors are orthogonal, and calculate the work done by a force on an object.

4. Can the dot product be negative?

Yes, the dot product can be negative. This occurs when the angle between the two vectors is greater than 90 degrees, resulting in a negative cosine value. A positive dot product indicates that the two vectors are pointing in the same general direction, while a negative dot product indicates they are pointing in opposite directions.

5. How is the dot product related to vector projection?

The dot product is used in the formula for vector projection, which is a method for finding the component of one vector in the direction of another vector. It is also used to calculate the magnitude of a vector projection.

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