One of Kepler's laws is that the orbits of planets are elliptical. It's not a suggestion.
BTW, circles are ellipses too, but so special that their likelihood is close to zero.
        
                    
             
        
        
        
The correct answer to the question is : D) Be moving at a constant velocity.
EXPLANATION:
As per Newton's first laws of motion, every body continues to be  at state of rest or of uniform motion in a straight line unless and until it is compelled by some external unbalanced forces acting on it.
Hence, it is the unbalanced force which changes the state of rest or motion of a body. Balanced force is responsible for keeping the body to be either in static equilibrium or in dynamic equilibrium.
As per the options given in the question, the last one is true for an object under balanced forces.
 
        
             
        
        
        
Answer = 330 m/s
The wave equation is as follows:
Wave speed = wavelength x frequency
The known values are:
Wavelength = 3m
Frequency = 110 Hz
Substitute the known values into the wave equation to find the wave speed.
Wave speed = 3 x 110
Wave speed = 330 m/s
        
             
        
        
        
Answer:



Explanation:
g = Acceleration due to gravity = 
 = Angle of slope =
 = Angle of slope = 
v = Velocity of child at the bottom of the slide
 = Coefficient of kinetic friction
 = Coefficient of kinetic friction
 = Coefficient of static friction
 = Coefficient of static friction
h = Height of slope = 1.8 m
The energy balance of the system is given by

The speed of the child at the bottom of the slide is 
Length of the slide is given by


The force energy balance of the system is given by

The coefficient of kinetic friction is  .
.
For static friction

So, the minimum possible value for the coefficient of static friction is  .
.