Question

un corp cu m=100g cade de la h=80 m
a)viteza cu care corpul cade
b)ce viteza are corpul dupa ce a parcurs 20m
c)la ce inaltime fata de sol energia cinetica este de 3 ori mai mare decat energia potentiala

Answer 1

Se da:
m=100g=0,1kg
h=80m
a)v=?m/s
b)Δh=20m; v1=?m/s
c)3Ep2=Ec2; h2=?m

Formule:
a)Ep=Ec
mgh=mv²/2
v=√2gh

b)Ec1+Ep1=Ep
mv1²/2+mgh1=mgh
v1²/2+g(h-Δh)=gh
v1²/2=gh-g(h-Δh)
v1²/2=g(h-h+Δh)
v1²/2=gΔh
v1=√2gΔh

c)3Ep2=Ec2
Ep2+Ec2=Ep
Ep2+3Ep2=Ep
4*mgh2=mgh
4*h2=h
h2=h/4

Calcule:
a)v=√2*10*80=40m/s
b)v1=√2*10*20=20m/s
c)h2=80/4=20m