m=4kg; v₀=0;F=10N; \(\mu\)=0,3; g=10m/s²; t=4s

F_ms=\(\mu.N=\mu.m.g\)=12N

F_hl=\(\left|F_k-F_{ms}\right|\)=2N

Theo DL 2 niutuon: a=\(\dfrac{F_{hl}}{m}\)=0,5m/s²

S=v₀t+\(\dfrac{at^2}{2}\)=4m

v=v₀+at=2m/s

m=2500N; t=60s; v₀=0; v=15m/s; \(\mu\)=0,02; g=10m/s²

a, a=\(\dfrac{v-v_0}{t}\)=0,25m/s²

S=v₀t+\(\dfrac{at^2}{2}\)=450m

b, F_k=\(\mu\).N=\(\mu\).m.g=500N

l₀=0,4m; l=0,45m; m=0,5kg; g=10m/s²

Vi vat treo thang dung

Co: P=F_dh\(\Leftrightarrow\)mg=K.\(\left|l-l_0\right|\)

\(\Leftrightarrow\)K=100N/m

A: vi am thanh ko the truyen trong moi truong chan ko nen ho phai dung micro va tai nghe

B:khi ho cham vao nhau mu bao ho cua ho vao nhau khi do am thanh co the truyen qua moi truong chat ran cho nen ho co the nghe thay nhau noi

v₁=50km/h; v₂=36km/h

AD cong thuc: v_tb=\(\dfrac{2v_1v_2}{v_1+v_2}\)\(\approx\)41,86km/s\(\approx\)11,63m/s

m=5kg; v₀=0; F=30N; \(\mu\)=0,4; g=10m/s²; S=16m

a,F_ms=\(\mu.N\)=20N

F_hl=10N

Theo dl 2 niuton: a=\(\dfrac{F_{hl}}{m}\)=2m/s²

b,Co: S= v₀t+\(\dfrac{at^2}{2}\)\(\Leftrightarrow\)t=4s

v=v₀+at=8m/s

t=1s; g=10m/s²

t=\(\sqrt{\dfrac{2h}{g}}\)\(\Leftrightarrow\)1=\(\sqrt{\dfrac{2h}{10}}\)\(\Rightarrow\)h=5m

Vay khi do cao = 6h

t=\(\sqrt{\dfrac{2h}{g}}\)=\(\sqrt{\dfrac{6\times5}{10}}\)=\(\sqrt{3}\)\(\approx\)1,73s

v₀=0; h=125m; g=10m/s²

a, t=\(\sqrt{\dfrac{2h}{g}}\)=5s

v=\(\sqrt{2gh}\)=50m/s

b,qd trong 3s: s=\(\dfrac{1}{2}\)gt²=45m

qd roi trong giay t3: s= 25m

c, \(\Delta\)s=h-s_t-1=(^{\(\dfrac{1}{2}\)}gt²)-(\(\dfrac{1}{2}\)g(t-1)²=45m

F₁=m₁g=3N

F₂=m₂g=4,5N

\(\Delta l_1\)=0,02m

\(\Delta l_2\)=\(\dfrac{F_2\Delta l_1}{F_1}\)=0,03m

v₀=5m/s; trong giay thu nhat t=1s; s=12m

a, S=v_ot+\(\dfrac{at^2}{2}\)\(\Leftrightarrow\)a=14m/s²

^{b, S=v}₀t+\(\dfrac{at^2}{2}\)=750m