Answer:
(E)56.0 m/s
Explanation:
Height =h=-160 m
Because the wallet moving in downward direction
Time=t=7 s
Final speed of wallet=v=0
We have to find the speed of helicopter ascending at the moment when the passenger let go of the wallet.
Where
Substitute the values
Option (E) is true
Answer:
steady state temperature =88.7deg C
t=time within 1 deg C of it steady state is 8.31s
Explanation:
A 1 m long wire of diameter 1mm is submerged in an oil bath of temperature 25-degC. The wire has an electrical resistance per unit length of 0.01 Ω/m. If a current of 100 A flows through the wire and the convection coefficient is 500W/m2K, what is the steady state temperature of the wire? From the time the current is applied, how long does it take for the wire to reach a temperature within 1-degC of the steady state value? The density of the wire is 8,000kg/m3, its heat capacity is 500 J/kgK and its thermal condu
The diameter of the wire is known to be=1mm
properties=
The density of the wire is 8,000 kg/m3,
heat capacity is 500 J/kgK
themal conductivity is 20W/m.K
electrical resistance per unit length of 0.01 Ω/m
from lump capavity method
500*(2.5*10^-4)/20
0.006<0.1
we know also, to find steady state temperature
Dh(T-Tinf)=
make T the subject of the equation , we have
T=25+
T=88.7 degC
rate of chnage in temperature
dT/dt=
at t=o and integrating both sides
we have
t=8.31s
steady state temperature =88.7deg C
t=time within 1 degC of it steady stae is 8.31s