Question

在离地面高15m处以30m/s的速度竖直向上抛出一物体,空气的阻力可以忽略g取10求1、在离地面

Answer 1

v0=30

v=v0-gt=30-10t

最高点 t=3,s=v0t-1/2gt^2=30*3-1/2 10 *3^2= 45m

h=15+s=60m

初始时 Ek0=1/2 mv^2 = 1/2 m* 30^2=450m

Ep=mgh=150m

E=Ep+Ek=600m

1.Ep'=Ek' = 1/2 E =300m

h'=Ep'/mg =300m/m*10 =30m

2.Ep' = 2/3E =400m

h'=Ep'/mg =400m/m*10 =40m