46 * Work-energy bar charts for a person going downstairs and upstairs are shown in Figure P7.46 . The bar charts show the average energy conversion across several steps. The system is the person, Earth, and the stairs. (a) What are the initial and final states in each case? (b) Describe and explain the similarities in the bar charts. (c) Describe the differences in the bar charts. How do these differences explain why we are less tired going downstairs? (d) How do you explain that when we walk upstairs | Δ U th | > | Δ U ch | , but when we walk downstairs | Δ U th | > | Δ U ch | ? (Hint: Think about what happens to our shoes and the stairs when we go downstairs.)
46 * Work-energy bar charts for a person going downstairs and upstairs are shown in Figure P7.46 . The bar charts show the average energy conversion across several steps. The system is the person, Earth, and the stairs. (a) What are the initial and final states in each case? (b) Describe and explain the similarities in the bar charts. (c) Describe the differences in the bar charts. How do these differences explain why we are less tired going downstairs? (d) How do you explain that when we walk upstairs | Δ U th | > | Δ U ch | , but when we walk downstairs | Δ U th | > | Δ U ch | ? (Hint: Think about what happens to our shoes and the stairs when we go downstairs.)
46 * Work-energy bar charts for a person going downstairs and upstairs are shown in Figure P7.46. The bar charts show the average energy conversion across several steps. The system is the person, Earth, and the stairs. (a) What are the initial and final states in each case? (b) Describe and explain the similarities in the bar charts. (c) Describe the differences in the bar charts. How do these differences explain why we are less tired going downstairs? (d) How do you explain that when we walk upstairs
|
Δ
U
th
|
>
|
Δ
U
ch
|
, but when we walk downstairs
|
Δ
U
th
|
>
|
Δ
U
ch
|
? (Hint: Think about what happens to our shoes and the stairs when we go downstairs.)
1. An arrangement of three charges is shown below where q₁ = 1.6 × 10-19 C, q2 = -1.6×10-19 C,
and q3 3.2 x 10-19 C.
2 cm
Y
93
92
91
X
3 cm
(a) Calculate the magnitude and direction of the net force on q₁.
(b) Sketch the direction of the forces on qi
(Figure 1)In each case let w be the weight of the suspended crate full of priceless art objects. The strut is uniform and also has weight w
Find the direction of the force exerted on the strut by the pivot in the arrangement (a).
Express your answer in degrees.
Find the tension Tb in the cable in the arrangement (b).
Express your answer in terms of w.
Find the magnitude of the force exerted on the strut by the pivot in the arrangement (b).
Express your answer in terms of w.
(Figure 1)In each case let ww be the weight of the suspended crate full of priceless art objects. The strut is uniform and also has weight w.
Find the direction of the force exerted on the strut by the pivot in the arrangement (b).
Express your answer in degrees.
Chapter 7 Solutions
Modified Mastering Physics with Pearson eText -- Access Card -- for College Physics: Explore and Apply (18-Weeks)
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