Answer:
The coupled velocity of both the blocks is 1.92 m/s.
Explanation:
Given that,
Mass of block A, 
Initial speed of block A, 
Mass of block B, 
Initial speed of block B, 
It is mentioned that if the two blocks couple together after collision. We need to find the common velocity immediately after collision. We know that due to coupling, it becomes the case of inelastic collision. Using the conservation of linear momentum. Let V is the coupled velocity of both the blocks. So,

So, the coupled velocity of both the blocks is 1.92 m/s. Hence, this is the required solution.
Answer:
The frequency of sound heard by the boy is 1181 Hz.
Explanation:
Given that,
Frequency of sound from alarm 
Speed = -8.25 m/s
Negative sign show the boy riding away from the car
Speed of sound = 343
We need to calculate the heard frequency
Using formula of frequency

Where,
= frequency of source
= speed of observer
= speed of source
= speed of sound
Put the value into the formula

here, source is at rest


Hence, The frequency of sound heard by the boy is 1181 Hz.
Atom A and atom C are the same element.
Answer:
8437.5
Explanation:
By applying the formula of kinetic energy:
Kinetic energy=1/2 mv^2
Why do transformers hum? Transformer noise is caused by a phenomenon which causes a piece of magnetic sheet steel to extend itself when magnetized. When the magnetization is taken away, it goes back to its original condition. This phenomenon is scientifically referred to as magnetostriction.