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Gravitation — Science STD 9 — Question

Gujarat BoardEnglish MediumSTD 9ScienceGravitation4 Marks
Question
The force acting on an object perpendicular to the surface is called thrust. When you stand on loose sand, the force, that is, the weight of your body is acting on an area equal to area of your feet. When you lie down then the same force acts on an area equalto the contact area of your whole body, which is larger than the area of your feet. Thus, the effects of forces of the same magnitude on different areas are different. In the above cases, thrust is the same. But effects are different. Therefore the effect of thrust depends on the area on which it acts. The effect of thrust on sand is larger while standing than while lying. The thrust on unit area is called pressure.Pressure=thrust/area. SI unit of pressure as $N/m^2$ or Pascal.
(i) SI unit of thrust is
$(a)$ m/s
$(b)$ $m/s^2$
$(c)$ Newton$(N)$
$(d)$ None of these
(ii) We have two different areas A and B. where A>B. Then relation between pressure on $A(P_A)$ and pressure on $B (P_B)$ is
$(a)$ $P_{A>}P_B$
$(b)$ $P_{B>}P_A$
$(c)$ $P_{A=}P_A$
$(d)$ None of these
(iii)SI unit of pressure is
$(a)$ $N/m^2$
$(b)$ Pascal.
$(c)$ Both $a$ and $b$
$(d)$ None of these
(iv) The effects of forces of the same magnitude on different areas are different. True or false
$(a)$ True
$(b)$ False
$(c)$ None of these
$(v)$ Define pressure.
✓

Answer

$(i)$ $c$
$(ii)$ $b$
$(iii)$ $c$
$(iv)$ $a$
$(v)$ pressure is defined as thrust or perpendicular force acting per unit area

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