Work - Example 7.1-3

 

Consider a block being pulled up a rough slope from position x₁ to position x₂.

 

 

In your book, draw a free-body diagram of the block. Click on the figure to see the results.

 

What is the resultant force F that acts on the particle?

 

F = (Pcosθ - mgsinφ - F_f ) i + (Psinθ + N - mgcosφ) j
F = (Pcosθ - mgsinφ - F_f ) i - (Psinθ + N - mgcosφ) j
F = P - mg - F_f

 

 

 

What is the work done by F on the particle?

 

U_1-2 = (Pcosθ + mgsinφ + F_f )(x₂ - x₁ )
U_1-2 = (Pcosθ - mgsinφ - F_f )(x₂ - x₁ )
U_1-2 = (Pcosθ - F_f )(x₂ - x₁ )

 

 

 

Which of the following statements are true?

Check all that apply.

 

The weight force of an object never does work.
Only the component of the force in the direction of the displacement does work.
The work done by a force F pointing in the opposite direction of the displacement Δx is negative.