Satellites are placed into orbit at least 150 km above Earth's surface to be above the atmosphere.
        
                    
             
        
        
        
<u>Answer:</u>
   Positive acceleration is in third hour and negative acceleration is in second hour.
<u>Explanation:</u>
   Velocity of car in first hour =  70 mph 
   Velocity of car in second hour = 60 mph
   Velocity of car in third hour = 80 mph
    Acceleration = Change in velocity / Time
    Acceleration in second hour = (60 - 70)/1 = -10 mph²
    Acceleration in third hour = (80 - 60)/1 = 20 mph²
    So positive acceleration is in third hour and negative acceleration is in second hour.
 
        
             
        
        
        
Answer:
The total work done by the two tugboats on the supertanker is 3.44 *10^9 J
Explanation:
The force by the tugboats acting on the supertanker is constant and the displacement of the supertanker is along a straight line.
The angle between the 2 forces and displacement is ∅ = 15°.
First we have to calculate the work done by the individual force and then we can calculate the total work.
The work done on a particle by a constant force F during a straight line displacement s is given by following formula:
W = F*s
W = F*s*cos∅
With ∅ = the angles between F and s
The magnitude of the force acting on the supertanker is F of tugboat1 = F of tugboat 2 = F = 2.2 * 10^6 N
The total work done can be calculated as followed:
Wtotal = Ftugboat1 s * cos ∅1 + Ftugboat2 s* cos ∅2
Wtotal = 2Fs*cos∅
Wtotal = 2*2.2*10^6 N * 0.81 *10³ m s *cos15°
Wtotal = 3.44*10^9 Nm = <u>3.44 *10^9 J</u>
<u />
The total work done by the two tugboats on the supertanker is 3.44 *10^9 J
 
        
             
        
        
        
Parallel circuits allow current to flow even if some paths are cut, because a parallel circuit has more than one current-carrying path through it.
 
        
                    
             
        
        
        
If she has a choice and the wiring details are stated on the packaging, 
then Janelle should look for lights that are wired in parallel within the 
string, and she should avoid lights that are wired in series within the string.  
If a single light in a parallel string fails, then only that one goes out.  
The rest of the lights in the string continue to shimmer and glimmer.
If a single light in a series string fails, then ALL of the lights in that string 
go out, and it's a substantial engineering challenge to determine which light 
actually failed.