Answer: 9.08KW and 16.21KW
Explanation:
The convection over a flat surface with a length of 10 m and a width of 6m.
The mean temperature is (5oC + 12oC)/2 = 8.5oC.
Then find the following properties of air at this temperature from Table A-15:
k = 0.02428 W/m(oC, v= 1.413x10-5 m2/s, and Pr = 0.7340.
find the Reynolds number. Re= VL/v
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This means that the flow becomes turbulent over the plate and we can use the Nusselt number equation for combined laminar and turbulent flow.
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We then use this Nusselt number to find the heat transfer coefficient and the heat transfer.
Check the screen shot for the calculation
Ans
9.08 kW
Then if the wind velocity were doubled, the Re number would be doubled and we would repeat the calculations above, starting with this revised Reynolds number..
Ans
16.21 kW
static friction is acting on stationery object (rest) but kinetic friction acting on a moving body.
The other one is static friction oppose the object to start a motion so it force is great than kinetic friction
Answer:
3) 255.04 m
Explanation:
Given:
v₀ = 115 km/h = 31.944 m/s
v = 0 m/s
a = -(4 m/s) / 2s = -2 m/s²
Find: Δx
v² = v₀² + 2aΔx
(0 m/s)² = (31.944 m/s)² + 2 (-2 m/s²) Δx
Δx = 255.11 m
Closest answer is option 3.
Compute first for the vertical motion, the formula is:
y = gt²/2
0.810 m = (9.81 m/s²)(t)²/2
t = 0.4064 s
whereas the horizontal motion is computed by:
x = (vx)t
4.65 m = (vx)(0.4064 s)
4.65 m/ 0.4064s = (vx)
(vx) = 11.44 m / s
So look for the final vertical speed.
(vy) = gt
(vy) = (9.81 m/s²)(0.4064 s)
(vy) = 3.99 m/s
speed with which it hit the ground:
v = sqrt[(vx)² + (vy)²]
v = sqrt[(11.44 m/s)² + (3.99 m/s)²]
v = 12.12 m / s
Define
m = the mass of the crate.
F = μmg, the resistive dynamic frictional force,
where μ =dynamic coefficient of friction.
a = the deceleration, when the crate slides subject only to to the frictional force.
The crate travels a distance d with initial velocity of v. Therefore
v² - 2ad = 0
a = v²/(2d) (1)
Also,
F = ma
F = (mv²)/(2d) (2)
When m is doubled, then
F = (2mv²)/(2d) = (mv²)/d
The corresponding deceleration is
a = F/m = v²/d
Therefore, the new distance traveled, D, is given by
v² - 2(v²/d)D = 0
D = d/2
The new distance traveled is one half of d.
Answer: d/2.
