题目内容

甲、乙两物体放在水平桌面上,甲的质量是乙的5倍,乙与桌面的接触面积是甲的4倍,则甲、乙两物体对桌面的压力之比为______,压强之比为______.若把甲置于乙上,则甲对乙的压强与乙对桌面的压强之比为______.
已知:m=5m,S=4S
(1)甲、乙对桌面的压力之比:
F
F
=
mg
mg
=
m
m
=
5m
m
=
5
1

对桌面的压强之比:
P
P
=
F
S
F
S
=
FS
FS
=
5
1
×
4
1
=
20
1

把甲置于乙上,甲对乙的压强与乙对桌面的压强之比:
P甲乙
P乙桌面
=
mg
S
(m+m)g
S
=
mS
(m+m)S
=
5m×4S
(5m+m)S
=
10
3
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