Well, since the question GIVES you the initial velocity, the acceleration, and the time, and ASKS for the final velocity, you'd be smart to find an equation that USES the initial velocity, the acceleration, and the time, and FINDS the final velocity.
Have a look at equation B ..... vf = vi + a*t . That's pretty durn close !
vf = (initial velocity) + (acceleration)*(time)
vf = (3 m/s) + (5 m/s²)*(4 sec)
vf = (3 m/s) + (20 m/s)
vf = 23 m/s
Answer: I think cars are designed to have crumble zone because lets say you're going 60-70 mph and you hit a brick wall that cant move, it would be a very hard jolt causing the beings inside to get thrown forward, but if it has a crumble zone it would slow the the jolt from is slowing down in the hit.
Well, those are good ones. Now how about a <u><em>thermometer</em></u> to <em>measure the temperature</em> ?
A ball falling through the air has a mass, a density, a volume...it is facing air resistance and is being acted on by gravity...it is accelerating and gaining velocity...and it is increasing in kinetic energy.
I suppose out of all those the biggest thing the ball has in this case is ENERGY. There are two main types to focus on...
Kinetic Energy - The further the ball fall the more KE it has...until terminal velocity is reach, then KE would become constant.
Potential Energy - Conversely to that of KE, the further the ball falls the less PE it will have.
<em>Heat/Thermal Energy is technically also present due to the friction from the air resistance, but the transfer of energy between the air and ball is quite complex and not necessary important for basic physics.
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The question itself seem kind of vague and open ended, but I could just be viewing it the wrong way.
Comment if you need more help!
