D is the best answer. In many physics problems we treat an extended object as if it were a point with the same mass located at the center of mass.
        
             
        
        
        
If the boat's speed is s, and the river's speed is r, and the boat is traveling east (0 degrees),
(0,r) + (s cos297,s sin297) = (6,0)
now just solve for r and s.
Pls mark me as brainliest
 
        
             
        
        
        
Answer:
C) rift valley 
Explanation:
A rift valley is a lowland region formed by the interaction of Earth's tectonic plates. This small rift valley has a typical formation—long, narrow, and deep. It was formed by the Thingvellir rift, where the North American and Eurasian tectonic plates are tearing, or rifting, apart over a hotspot on the island of Iceland. 
 
        
                    
             
        
        
        
Answer:
a)  , b)
, b)  , c)
, c) 
Explanation:
a) The change in the gravitational potential energy of the marble-Earth system is:


b) The change in the elastic potential energy of the spring is equal to the change in the gravitational potential energy, then:

c) The spring constant of the gun is:




 
        
             
        
        
        
Answer:
C. 
Explanation:
Exothermic refers to a RELEASE of energy through a reaction(usually chemical). When salt dissociates, polar water molecules pull apart ions, releasing energy.