At a definite point, the bridge would begin oscillating to the matching rhythm as that
of the marching footsteps.
This oscillation would touch a determined peak when the bridge can
no longer tolerate its own
power and later collapses. So, soldiers are
systematic to break their steps
while passing a bridge.
 
        
                    
             
        
        
        
The work done on the car is -20 J.
Work done on the car is negative, meaning that the car actually does work on the external system.
<h3>Energy and law of conservation of energy</h3>
- Energy is the ability to do work
- the law of conservation of energy states that the total energy in a system is conserved
From the law of conservation of energy, the initial energy of the car before it moves down the road remains constant or unchanged. 
- Initial energy = 100 J
- Initial energy = Final energy - work done on car
- Final Energy = Work done on car + initial energy
80J = Work done on car + 100 J
Work done on car = 80 - 100J
Work done on car = -20 J
Hence, the work done on the car is -20 J
Work done on car is negative.
Since work done on the car is negative, it means that the car actually does work on the external system. Hence, the decrease in the energy of the car.
Learn more about energy and work at: brainly.com/question/13387946
 
        
             
        
        
        
Answer:
modem, digital music players, optical communication
Explanation:
Photos of devices are attached. An example of R2R logic circuit is also attached. DAC conversion is also done via pulse code modulation
 
        
             
        
        
        
The element would have 52 protons because atomic number gives protons.
        
                    
             
        
        
        
Answer:
power=work done÷time taken
2×5=10
10÷10=1
ans 1J per second