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Ad libitum [116K]
3 years ago
15

A passenger in a train accelerating smoothly away from a station observes that a child’s yo-yo hanging by its string from a lugg

age rack makes a 10 degree angle from the vertical. Calculate the train’s acceleration?
Calculate the radius of a solid iron sphere that will have a terminal velocity of 100 m/s when dropped from a large height.

Density of iron is 7874 kg/m3. A sphere has Cd = .47. Use p = 1.3kgm3 for air
Physics
1 answer:
olchik [2.2K]3 years ago
3 0

Answer:

1.73 m/s²

3.0 cm

Explanation:

Draw a free body diagram of the yo-yo.  There are two forces: weight force mg pulling down, and tension force T pulling up 10° from the vertical.

Sum of forces in the y direction:

∑F = ma

T cos 10° − mg = 0

T cos 10° = mg

T = mg / cos 10°

Sum of forces in the x direction:

∑F = ma

T sin 10° = ma

mg tan 10° = ma

g tan 10° = a

a = 1.73 m/s²

Draw a free body diagram of the sphere.  There are two forces: weight force mg pulling down, and air resistance D pushing up.  At terminal velocity, the acceleration is 0.

Sum of forces in the y direction:

∑F = ma

D − mg = 0

D = mg

½ ρₐ v² C A = ρᵢ V g

½ ρₐ v² C (πr²) = ρᵢ (4/3 πr³) g

3 ρₐ v² C = 8 ρᵢ r g

r = 3 ρₐ v² C / (8 ρᵢ g)

r = 3 (1.3 kg/m³) (100 m/s)² (0.47) / (8 (7874 kg/m³) (9.8 m/s²))

r = 0.030 m

r = 3.0 cm

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Consider a cube with one corner at the origin and with sides of length 50 cm positioned along the x y z axes. There is an electr
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E → = < 45, 210 y , 0 > N/C

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To find the charge in the cube, we need the net flux in the cube

In the z-direction, the electric field is 0, no, net flux in that direction,

In the x-direction, the electric field is constant, the same flux thay enters the face at x = 0 is the same that leaves at x= 0

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Φ = Q/ε₀

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ε₀ = (8.85 × 10⁻¹²) C²N·m².

Q = Φε₀ = 26.25 × 8.85 × 10⁻¹²

Q = (2.323 × 10⁻¹⁰) C

Hope this Helps!!!

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4 years ago
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