The trains take <u>57.4 s</u> to pass each other.
Two trains A and B move towards each other. Let A move along the positive x axis and B along the negative x axis. 
therefore,

The relative velocity of the train A with respect to B is given by,

If the train B is assumed to be at rest, the train A would appear to move towards it with a speed of 170 km/h. 
The trains are a distance d = 2.71 km apart.
Since speed is the distance traveled per unit time, the time taken by the trains to cross each other is given by,

Substitute 2.71 km for d and 170 km/h for 

Express the time in seconds.

Thus, the trains cross each other in <u>57.4 s</u>.
 
        
             
        
        
        
If 50 identical light bulbs are connected in series across 
a single power source, then the voltage across each bulb 
is ( 1/50 ) of the voltage delivered by the power source.
        
                    
             
        
        
        
Answer:
0.1 m
Explanation:
F = Force exerted on spring = 3 N
k = Spring constant = 60 N/m
x = Displacement of the block
As the energy of the system is conserved we have




The position of the block is 0.1 from the initial position.
 
        
             
        
        
        
Explanation:
Average speed = distance / time
|v| = (7 km + 2 km) / (2 hr + 1 hr)
|v| = 3 km/hr
Average velocity = displacement / time
v = (7 km east + 2 km east) / (2 hr + 1 hr)
v = 3 km/hr east
 
        
             
        
        
        
Answer:
Pressure of the gas = 12669 (Pa) and height of the oil is 1,24 meters
Explanation:
First, we can use the following sketch for an easy understanding, in the attached image we can see the two pressure gauges the one with mercury to the right and the other one with oil to left. We have all the information needed in the mercury pressure gauge, so we can determine the pressure inside the vessel because the fluid is a gas it will have the same pressure distributed inside the vessel (P1).
Since P1 = Pgas, we can use the same formula, but this time we need to determine the height of the column of oil in the pressure gauge.
The result is that the height of the oil column is higher than the height of the one that uses mercury, this is due to the higher density of mercury compared to oil.
Note: the information given in the units of the fluids is not correct because the density is always expressed in units of (mass /volume)