Answer:
his feet feel warmer because of friction. when friction takes place then an object will warm up because friction is a universal law that always takes place. if you rub your hands together, you also experience the heat of frictional I hope that helped.
 
        
             
        
        
        
Answer:
t = 4.0 min
Explanation:
given data:
diameter of rod = 2 cm
T_1 = 100 degree celcius
Air stream temperature =  20 degree celcius
heat transfer coefficient = 200 W/m2. K
WE KNOW THAT
copper thermal conductivity = k = 401 W/m °C
copper specific heat Cp = 385 J/kg.°C
density of copper = 8933 kg/m3 
charateristic length is given as Lc 




 
Biot number is given as 

Bi = 0.0025
As Bi is greater than 0.1 therefore lumped system analysis is applicable
so we have
 ............1
 ............1
where b is given as



b = 0.01163 s^{-1}
 putting value in equation 1 

solving for t we get
t = 4.0 min
 
        
             
        
        
        
Answer:

Explanation:
<u>Work and Kinetic Energy
</u>
The work an object does due to its motion is equal to the change of its kinetic energy. Being ko and k1 the initial and final kinetic energy respectively and m the mass of the object, then

Since

We have

The truck has a mass of 60,000 kg and is moving at 27 m/s. The runaway truck ramp must stop the truck, so the final speed is 0. Thus



 
        
             
        
        
        
Answer:
option D
Explanation:
given,

increase the intensity by factor of 9
     I₁ = I₀
     I₂ = 9 I₀
 now,
 
 
 
 
       A₂ = 3 A₁
hence, amplitude increase with the factor of 3
so, the correct answer is option D
 
        
                    
             
        
        
        
Answer:
force (tension) of 29.4 N (upward)  in 100 cm
force (tension) of 58.4 N (upward)  in 200 cm
Explanation:
Given: 
Length of tube = 5 m (500 cm)
Mass of tube = 9 
Suspended vertically from 150 cm and 50 cm.
Computation:
Force = Mass × gravity acceleration.
Force = 9.8 x 9 
Force = 88.2 N
So,
Upward forces = Downward forces
D1 = 150 - 50 = 100 cm
D2 = 150 + 50 = 200 cm
And F1 = F2
F1 x D1 = F2 x D2
F1 x 100 = F2 x 200
F = 2F
Total force = Upward forces + Downward forces
3F = 88.2
F = 29.4 and 2F = 58.8 N
force (tension) of 29.4 N (upward)  in 100 cm
force (tension) of 58.4 N (upward)  in 200 cm