For example, suppose a 100 kg object accelerates to 10 m/s, does that mean I should use momentum or kinetic energy (with momentum I get 1000 and KE 5000)? When the object reached a speed of 5 m/s, 1250 joules was used according to the kinetic formula. If the object accelerated an additional 5 m/s, it has used a total of 5000 joules (so an extra 3750). It is not normal that for the same speed change 3 times more energy is consumed? this means that a constant energy supply is not equal to a constant acceleration, which I find strange.
Answer
the kinetic energy that the object has when it moves 10 m/s is indeed 5000 J.
If the object accelerates to 5 m/s it has an energy of 1250 J. To accelerate further to 10 m/s it has an energy of:
5000 – 1250 J needed, so 3750 J extra. And in the end the object has the same energy, namely 5000 J at a speed of 10 m/s.
Answered by
dr. Annick Van Deynse
http://www.ugent.be
.