Question

1. O forta de 50N acționeaza asupra unui resort elastic , alumgindu-l cu 10 cm. Care va fi elongatia daca forta aplucata creste de 5 ori?

2. O forta de tractiune de 25 N produce o crestere a vitezei intre 54km/h si 72km/h intr-un minut si 40 de secunde. Calculati forta de frecare (m=100kg)
VAA ROOOG !

Answer 1

1.F=kx
x=10cm=0.1 m
k=F/x => k=50 N / 0.1 m=500 N/m
5F=kx'
x'=5F/k => x'=250 N / 500 N/m = 0.5 m = 50 cm

2. a=(v2-v1)/t   
v2-v1=72-54=18 km/h=5 m/s 
1min 40 s=100s
a=5/100 m/s^2 = 0.05 m/s^2
F-Ff=ma | +Ff - ma
Ff=F-ma
Ff=25 - 100×5/100= 20 N