Infrared light
it is also found under the name IR lights. although it’s technically invisible, it can still be seen with machinery up to at least 1050 nm in experiments.
        
             
        
        
        
Answer:
1) 0.43 meters per second
2) 0.21 meters per second 
3) 1.02 
4) 0.66 seconds
Explanation:
part 1
By conservation of energy, the maximum kinetic energy (K) of the block is at equilibrium point where the potential energy is zero. So, at the equilibrium kinetic energy is equal to maximum potential energy (U):


With m the mass, v the speed, k the spring constant and xmax the maximum position respect equilibrium position. Solving for v

part 2 
Again by conservation of energy we have kinetic energy equal potential energy:


part 3 
Acceleration can be find using Newton's second law:

with F the force, m the mass and a the acceleration, but elastic force is -kx, so:


part 4
The period of an oscillator is the time it takes going from one extreme to the other one, that is going form 4.5 cm to -4.5 cm respect the equilibrium position. That period is:

So between 0 and 4.5 cm we have half a period:

 
        
             
        
        
        
You didn't actually include the speed of sound. But it doesn't matter for this question. If the trumpeter and the listener are on the same moving sidewalk then the distance between them is not changing. The Doppler shift only happens when the distance between the source and the Observer is changing. So the Listener hears the same 290 Hertz that the trumpeter is generating.
        
             
        
        
        
A load of 20N is lifted through a height of 8m by a machine.If the effort of 80N moves a distance of 6m.Calculate the efficiency percentage of the machine
Explanation:
A load of 20N is lifted through a height of 8m by a machine.If the effort of 80N moves a distance of 6m.Calculate the efficiency percentage of the machine