Answer:
Velocity of ball B after impact is 
and ball A is 
Explanation:
= Initial velocity of ball A
= Initial velocity of ball B = 0
= Final velocity of ball A
= Final velocity of ball B
= Coefficient of restitution = 0.8
From the conservation of momentum along the normal we have
Coefficient of restitution is given by
Adding the above two equations we get
From the conservation of momentum along the plane of contact we have
Velocity of ball B after impact is and ball A is .
Answer: a) 1.05kW b) 3.78MJ c) 5.3 bars
Explanation :
A)
Conversions give 900 kcal as 900000 x 4.2 J/cal {4.2 J/cal is the standard factor}
= 3780kJ
And 1 hour = 3600s
Therefore, Power in watts = 3780/3600 = 1.05kW = 1050W
B)
At 15km/hour a 15km run takes 1 hour.
1 hour is 3600s and the runner burns 1050 joule per second.
Energy used in 1 hour = 3600 x 1050 J/s
= 3780000 J or 3.78MJ
C)
1 mile = 1.61km so 13.1 mile is 13.1 x 1.61 = 21.1km
15km needs 3.78 MJ of energy therefore 21.1km needs 3.78 x 21.1/15 = 5.32MJ =5320 kJ
Finally,
1 Milky Way = 240000 calories = 4.2 x 240000 J = 1008000J or 1008kJ
This means that the runner needs 5320/1008 = 5.3 bars
Answer:
V = 6.33 m/s
Explanation:
Given:
- The length of the wire L = 0.02 m
- The diameter of the wire D = 0.0005 m
- The calibration expression V = 0.0000625*h^2
- Environment temperature T_inf = 298 K
- Surface temperature T_s = 348 K
- The voltage drop dV = 5 V
- The electric current I = 0.1 A
Find:
- the velocity of Air
Solution:
- Calculate the surface area of the wire:
A = pi*D*L
A = pi*(0.0005)*(0.02) = 0.00003142 m^2
- The rate of energy in the wire P:
P = I*dV = 0.1*5 = 0.5 W
- Apply Newton's Law of Cooling:
P = h*A*(T_s - T_inf)
h = P /A*(T_s - T_inf)
Plug in the values:
h= 0.5/ 0.00003142*(348 - 298)
h = 318.27 W /m^2K
- Using the calibration relationship given, compute the velocity of air:
V = 6.25*10^-5 * h^2
V = 6.25*10^-5 * (318.27)^2
V = 6.33 m/s
