Answer:
Explanation:
Given
there is fix Quantity of gas i.e. mass of gas is constant
From ideal gas Equation
PV=nRT
(a) volume always increases is not true as Pressure can also be increased .
(b)If Pressure is constant along with mass then as Temperature increases, Volume also increases.
(c)true , Product of Pressure and volume depends upon temperature thus it also increases with temperature.
(d)Density of gas may or may not increases
As density is 
volume may increase or decrease as temperature increase .
(e)false
as it clearly stated that quantity of fixed therefore there is no change in gas
To solve this problem it is necessary to apply the concepts related to Dopler's Law. Dopler describes the change in frequency of a wave in relation to that of an observer who is in motion relative to the Source of the Wave.
It can be described as

c = Propagation speed of waves in the medium
= Speed of the receiver relative to the medium
= Speed of the source relative to the medium
Frequency emited by the source
The sign depends on whether the receiver or the source approach or move away from each other.
Our values are given by,
Velocity of car
velocity of motor
Velocity of sound
Frequency emited by the source
Replacing we have that



Therefore the frequency that hear the motorcyclist is 601.7Hz
Here as we know that there is no loss of energy
so we can say that maximum kinetic energy will become gravitational potential energy at its maximum height
So here we have

here we have
v = 20 m/s
m = 8000 kg
now from above equation we have



so maximum height is 20.4 m
The correct answer is
C ). A hypothesis includes an explanation for why two variables affect each other, but a law only describes how they affect each other.
Given :
A mover slides a refrigerator weighing 650 N at a constant velocity across the floor a distance of 8.1 m.
The force of friction between the refrigerator and the floor is 230 N.
To Find :
How much work has been performed by the mover on the refrigerator.
Solution :
Since, refrigerator is moving with constant velocity.
So, force applied by the mover is also 230 N ( equal to force of friction ).
Now, work done in order to move the refrigerator is :

Hence, this is the required solution.