I think you're saying that once you start pushing on the cars, you want to be able to stop each one in the same time.  
This is sneaky.  At first, I thought it must be both 'c' and 'd'.  But it's not 
kinetic energy, for reasons I'm not ambitious enough to go into.
(And besides, there's no great honor awarded around here for explaining 
why any given choice is NOT the answer.) 
The answer is momentum.
Momentum is (mass x speed).  Change in momentum is (force x time).
No matter the weight (mass) or speed of the car, the one with the greater 
momentum is always the one that will require the greater (force x time)
to stop it.  If the time is the same for any car, then more momentum
will always require more force.
        
             
        
        
        
Answer:
The helicopter was deformed and destroyed in the inelastic collision.
Explanation:
- When two object collide there exist two way of colliding: elastic collision and inelastic collision.
- Two terms are considered during the collision: kinetic energy and momentum.
- If both of these terms are conserved in any collision then there is no significant loss of property, this is called as elastic collision.
- If only momentum is conserved but kinetic energy is converted into other forms then it is inelastic collision. In inelastic collision, the energy is lost in the form of vibration, sound etc. causing the damage to colliding object.
- Hence the deformation of helicopter was due to inelastic collision. 
 
        
             
        
        
        
The wavelength of the light decreases as it enters into the medium with the greater index of refraction. The wavelength of the light remains constant as it transitions between materials.