Answer:
The objects must be different temperatures.
Explanation:
For heat to flow between two objects, heat must be flowing between them. The thermal gradient allows for the flow of heat. Heat is a form of energy that is dissipated from one place to another based on temperature difference.
Temperature is the degree of hotness or coldness of body. It is power by heat energy between two bodies.
Heat generally flows from a body at high temperature to one at low temperature. When thermal equilibrium is established and both bodies have the same temperature, heat will stop to flow.
Answer:
a. wavelength of the sound, 
b. observed frequecy, 
Given:
speed of sound source,
= 80 m/s
speed of sound in air or vacuum,
= 343 m/s
speed of sound observed,
= 0 m/s
Solution:
From the relation:
v =
(1)
where
v = velocity of sound
= observed frequency of sound
= wavelength
(a) The wavelength of the sound between source and the listener is given by:
(2)
(b) The observed frequency is given by:


(3)
Using eqn (2) and (3):


pitch goes up on approach ... Doppler effect
Answer:
Explanation:
The condition for translation equilibrium is that is that the net force acting on the body must be zero.
The sum all the external forces acting on the body in horizontal as well as vertical direction must be zero.
∑Fₓ=0 and ∑Fy=0
now if the above two condition are satisfied the rigid body is said to be in translational equilibrium.
God bless... hope this help to clear your doubt.