Answer:
An unbalanced force (net force) acting on an object changes its speed and/or direction of motion. ... A net force = unbalanced force. If however, the forces are balanced (in equilibrium) and there is no net force, the object will not accelerate and the velocity will remain constant.
Explanation:
 
        
             
        
        
        
Force , F = ma
F =  m(v - u)/t                
Where m = mass in kg, v= final velocity in m/s, u = initial velocity in m/s
t = time, Force is in Newton.
m= 1.2*10³ kg,  u = 10 m/s,  v = 20 m/s, t = 5s
F =  1.2*10³(20 - 10)/5
F = 2.4*10³ N = 2400 N
        
             
        
        
        
A motor is built to use all those things and produce mechanical energy.
        
                    
             
        
        
        
Answer:
Time period of the motion will remain the same while the amplitude of the motion will change
Explanation:
As we know that time period of oscillation of spring block system is given as

now we know that
M = mass of the object
k = spring constant
So here we know that the time period is independent of the gravity
while the maximum displacement of the spring from its mean position will depends on the gravity as


so we can say that
Time period of the motion will remain the same while the amplitude of the motion will change
 
        
             
        
        
        
C is the answer to your question.