物理力學一問

Assume there is no frictions,

then Change of Kinetic Energy of the bullet=Work done added on the borad
1/2mv^2=Fd
1/2mv^2=mad
1/2(500)^2=800000 d
d=0.15625 (m)=15.625cm

in order to not passing through the wall, the thickness must be greater than 15.625cm

子彈以500ms^-1的速率射向一道木牆

它在牆壁內的匀減速度是800000ms^-2。

子彈冇穿木牆,牆有幾厚？？


by

s = v^2 - u^2 / 2a

s = -500^2 / -2(800000)

s = 0.15625m

so,

s = 15.6cm