Question

Un corp cu masa m=1 kg se misca uniform accelerat fara viteza initiala parcurgand in prima secunda distanta d1=1 m.Sa se afle energia cinetica a corpului dupa 2 secunde. Daca se poate cat mai explicit,va multumesc!

Answer 1

Deoarece corpul se misca uniform accelerat din repaus , acceleratia medie coincide cu cea instantanee , astfel ca $a_{m}$=a=$\frac{delta v}{delta t}$=$\frac{v}{t}$⇒v=a*t , iar distanta parcursa este:d=$v_{m}$*t=$\frac{v}{2}$*t=$\frac{a* t^{2} }{2}$⇒a=$\frac{2* d_{1} }{ t ^ {2} _{1} }$=$\frac{2*1}{1*1}$=2 m/$s^{2}$
Cand $t_{2}$=2s , $v_{2}$=a*$t_{2}$=$\frac{2* d_{1} }{ t_{1 } ^{2} }$*$t_{2}$=$\frac{2*1}{1*1}$*2=2*2=4 m/s
$E_{c}$=$\frac{m* v^{2} _{2} }{2}$=$\frac{1*4*4}{2}$=$\frac{16}{2}$=8J