Fertility is
2 answers:
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Answer:
3.26 secs
Explanation:
Diameter of sphere ( D )= 10 mm
T1 = 75°C
P = 1 atm
T∞ = 23°C
T2 = 35°c
Velocity = 10 m/s
<u>Determine how long it will take to cool the sphere to 35°C</u>
<em>Using the properties of copper and air given in the question</em>
Nu = 2 + (Re)^0.8 (Pr)^0.33
hd / k = 2 + ( vd/v )^0.8 (Pr)^0.33
∴ h ≈ 2594.7 W/m^2k
Given that :
(T2 - T∞) / ( T1 - T∞ ) = exp [ ( -hA / pv CP ) t ]
( 35 - 23 ) / ( 75 - 23 ) = exp [ - 2594.7 * 6 * t / 8933 * 387 * 10 * 10^-3 ]
= ln ( 12/52 ) = -1.466337069 = - 0.45032919 * t
∴ t ≈ 3.26 secs ( -1.466337069 / -0.45032919 )
Answer:
<em>We need to (at least) apply a force of 9.8 N to move the block</em>
Explanation:
<u>Second Newton's Law</u>
If a net force different from zero is applied to an object of mass m, then it will move at an acceleration a, given by
If we apply a force F to an object placed on a rough surface, the only way to make it move is to beat the friction force which is given by
Where is the static friction coefficient and
is the normal force exerted by the table to the object. Since there is no motion in the vertical direction the normal force equals the weight of the object:
The friction force is
Thus, we need to (at least) apply a force of 9.8 N to move the block
Answer:
10.84 m/s2 radially inward
Explanation:
As the car is traveling an a constant tangential speed of 80.8 m/s, the total acceleration only consists of the centripetal acceleration and no linear acceleration. The formula for centripetal acceleration with respect to tangential speed v = 80.8 m/s and radius r =602 m is
b) The direction of this centripetal acceleration is radially inward