a, Wt0=mgh=20(J)
Wđ=1/2mv(2)cđ=1/2.0,2.2.10.10=20(J)
=>Wđ=Wt0
b, Ta có:Wđ=Wt
Mà W=Wt0
W=2Wt=2mgh=2.10.0,2.h=20
=>h=5(m)

Ta có:Fms=mgsin-ma(ADDL2N)
v2-v02=2as
=>a=(6(2)-2(2)):(2.8)=2(m/s2)
a, Ap=Psins=mgsins=1,5.10.sin30.8=60(J)
b, Afms=-(mgsin-ma)s=-(1,5.10.sin30-1,5.2).8=-36(J)

A=1200.5=6000(J)
Aci=6000.80%=4800(J)
Mà Aci=P.h=mgh
(=)h=Acimg=4800.10.300=1,6(m)

a,
A=100.15=1500(J)
(P)=1500:15=100(W)
b,
A=10.100.cos45=707,1(sấp xỉ)(J)
(P)=Ans:10=70,71(sấp xỉ)(W)

Ta có:W=Wt+Wđ=mgh+1/2mv(2)
Mà khi h=3 m thì Wđ=1,5Wt
=>W=2,5Wt=2,5.m.3.10=37,5
(=)m=0,5(kg)
Ta có:1/2mv(2)=1,5mgh
(=)v(2)=(1,5.10.3):1/2=90
(=)v=3 căn 10(m/s)

a, v=v0+at
a=(v-v0):t
a=6:15=0,4(s)
F kéo=0,4.2000=800(N)
S=v0t+1/2at(2)=1/2.0,4.15(2)=45(m)
A=800.45=36000(J)
(P)=A/t=36000:15=2400(W)
b, Fms=0.05.2000.10=1000(N)
Ta có: F-Fms=ma
=>F=Fms+ma=1000+2000.0.4=1800(N)
A=1800.45=81000(J)
(P)=A/t=81000:15=5400(W)