Pressure - AP Physics 1

A student holds a thumbtack and presses it into a cork with the same $10\,\text{N}$ force. The tack's point area is $1.0\times10^{-6}\,\text{m}^2$ and the flat head area is $1.0\times10^{-4}\,\text{m}^2$ . Pressure is due to contact force. Where is the pressure greater?
Answer: At the point, because the same force acts on a much smaller area This question tests understanding of pressure as force per unit area. Pressure is P = F/A, where the same 10 N force is applied at both the point and head of the thumbtack. The point has an extremely small area (1.0×10⁻⁶ m²) while the head has a much larger area (1.0×10⁻⁴ m²), which is 100 times larger. This means the pressure at the point is 100 times greater than at the head, explaining why the point penetrates the cork while the head doesn't hurt the thumb. Choice C incorrectly assumes equal force means equal pressure everywhere. When analyzing pressure in tools like tacks or nails, the dramatic area difference creates the useful pressure concentration.
In a tank of oil, pressure is due to fluid depth. Point $A$ is $0.30\,\text{m}$ below the surface and point $B$ is $0.80\,\text{m}$ below. Which comparison is correct?
Answer: $p_B>p_A$ because pressure increases with depth. This question tests understanding of pressure variation with depth in fluids. In any static fluid, pressure increases with depth according to P = P₀ + ρgh, where h is the depth below the surface. Point B at 0.80 m depth experiences greater pressure than point A at 0.30 m depth because there is more fluid weight above it. Choice A incorrectly reverses this relationship, perhaps confusing proximity to surface with lower pressure. When analyzing fluid pressure, remember that pressure always increases with depth regardless of container shape or fluid type.
A sealed container holds water at rest. Point A is $0.20\,\text{m}$ below the surface; point B is $0.50\,\text{m}$ below the surface. Pressure is due to fluid depth. Which point has greater water pressure?
Answer: Point B, because pressure increases with depth This question assesses understanding of hydrostatic pressure in fluids, which increases with depth. In a fluid at rest, pressure at a depth h is P = ρgh + P_atm, where ρ is density, g is gravity, and h is depth, showing pressure grows linearly with depth. Point A at 0.20 m has less pressure than Point B at 0.50 m due to the greater overlying fluid weight at B. Thus, Point B experiences greater water pressure. Distractor C suggests equal pressure because the container is sealed, but sealing does not affect the depth dependence. A useful strategy is to compare depths directly, as pressure differences depend solely on Δh in the same fluid.
A $12\,\text{N}$ book rests on a table. It can lie flat with contact area $0.060\,\text{m}^2$ or on its side with contact area $0.020\,\text{m}^2$ . Pressure here is due to contact force distributed over area. Which orientation produces greater pressure on the table?
Answer: On its side, because the same force acts on a smaller area This question assesses understanding of pressure as force per unit area in contact scenarios. Pressure is defined as the force applied perpendicular to a surface divided by the area over which it is distributed, P = F/A. For the book weighing 12 N, when lying flat with a larger contact area of 0.060 m², the pressure is lower compared to when it is on its side with a smaller area of 0.020 m². Since the force (weight) remains constant, the orientation with the smaller area produces greater pressure, which is the case when the book is on its side. A common distractor is choice C, which incorrectly states that both orientations produce the same pressure because the weight is unchanged, ignoring the role of contact area. To approach similar problems, always calculate pressure using P = F/A and compare values based on varying areas for constant force.
A rectangular block is pushed against a wall with a horizontal contact force of $60\,\text{N}$ . In case 1, it contacts over $0.030\,\text{m}^2$ ; in case 2, it contacts over $0.010\,\text{m}^2$ . Pressure is due to contact force over area. Which case produces greater pressure on the wall?
Answer: Case 2 This question assesses pressure from contact force over area in AP Physics 1. Pressure is defined as P = F/A, where the same force over a smaller area produces higher pressure. The force is 60 N in both cases, but case 2 has one-third the area of case 1, tripling the pressure. Thus, case 2 has greater pressure on the wall. Choice C distracts by focusing only on equal forces, neglecting the inverse relation to area. A transferable strategy is to use P = F/A to quantify and compare pressures in different contact scenarios.
Two points are in the same still water column open to the atmosphere. Point A is $0.30\,\text{m}$ below the surface and point B is $0.30\,\text{m}$ below the surface but at a different horizontal location. Pressure is due to fluid depth. How do the pressures compare?
Answer: $P_A=P_B$ , because pressure depends only on depth in a static fluid This question tests understanding that pressure depends only on depth in a static fluid. In any static fluid, pressure at a given depth is P = P₀ + ρgh, which depends only on the vertical depth h below the surface, not on horizontal position. Since both points A and B are at the same 0.30 m depth, they experience identical pressure regardless of their horizontal separation or position relative to container walls. This principle allows pressure to be transmitted equally throughout a fluid at the same depth. Choice A incorrectly suggests that being "directly under" matters, confusing vertical depth with horizontal position. When analyzing fluid pressure, only the vertical depth below the surface determines the pressure value.
A beaker contains water at rest. Point $G$ is $0.40\,\text{m}$ below the surface and point $H$ is $0.80\,\text{m}$ below; pressure is due to fluid depth. Which pressure is larger?
Answer: $P_H>P_G$ because pressure increases with depth This question tests understanding of pressure increasing with depth in fluids. In static water, pressure follows P = P_surface + ρgh, where h is depth below surface. Point G at 0.40 m depth has pressure $P_G$ = $P_0$ + ρg(0.40), while point H at 0.80 m depth has pressure $P_H$ = $P_0$ + ρg(0.80). Since 0.80 > 0.40, point H experiences greater pressure from the taller column of water above it. The pressure difference is ΔP = ρg(0.80 - 0.40) = 0.40ρg. Choice D incorrectly claims equal pressure, confusing force with pressure. Remember that in any fluid at rest, pressure always increases linearly with depth.
A student presses two solid blocks on a table. Block 1 has contact area $0.020\,\text{m}^2$ and Block 2 has $0.010\,\text{m}^2$ . Each exerts a downward contact force of $40\,\text{N}$ . Pressure is due to contact force over area. Which surface experiences greater pressure?
Answer: Block 2 This question assesses the concept of pressure in AP Physics 1, specifically how it relates to contact force and area. Pressure is defined as the force applied per unit area, so P = F/A. For solid objects pressing on a surface, a smaller contact area results in higher pressure when the force is constant. Both blocks exert 40 N, but Block 2 has half the area of Block 1, doubling its pressure. Choice C is a common distractor because it confuses equal forces with equal pressures, ignoring the role of area. A transferable strategy is to always calculate P = F/A explicitly when comparing pressures from contact forces.
In a lake, pressure is due to fluid depth. At points $P$ and $Q$ , $Q$ is $2.0\,\text{m}$ deeper than $P$ . Which is true?
Answer: $p_Q>p_P$ because pressure increases with depth in a fluid at rest. This question tests understanding of pressure variation with depth in fluids. In a static fluid, pressure increases linearly with depth according to P = P₀ + ρgh, where ρ is fluid density, g is gravitational acceleration, and h is depth below the surface. Since point Q is 2.0 m deeper than point P, the pressure at Q must be greater than at P due to the additional weight of water above it. Choice B incorrectly suggests equal pressures, confusing the fact that pressure acts in all directions with pressure magnitude. When comparing pressures in fluids, always consider the depth difference and remember that deeper points have higher pressure.
A $300\,\text{N}$ machine rests on four identical feet. Each foot has area $2.0\times10^{-3}\,\text{m}^2$ ; pressure is due to contact force. Compared to one foot supporting the full weight, the pressure is
Answer: four times smaller, because the force per foot is smaller while area per foot is the same This question tests understanding of pressure distribution across multiple contact points. When the 300 N machine rests on four identical feet, each foot supports 300 N / 4 = 75 N. The pressure at each foot is P = 75 N / (2.0×10⁻³ m²) = 37,500 Pa. If one foot supported the full weight, pressure would be 300 N / (2.0×10⁻³ m²) = 150,000 Pa, which is four times larger. The four-foot configuration reduces pressure to one-fourth because each foot carries one-fourth the force while maintaining the same contact area. Choice A incorrectly multiplies by the number of feet. When weight is distributed across multiple supports, divide the total force by the number of supports to find force per support.
An open container holds oil. Point R is $0.10\,\text{m}$ below the oil surface; point S is $0.40\,\text{m}$ below the surface. Pressure is due to fluid depth. Which point has greater pressure in the oil?
Answer: Point S, because pressure increases with depth This question tests understanding of pressure increasing with fluid depth. Pressure in a static fluid follows P = P₀ + ρgh, where ρ is the oil's density and h is depth. Point S at 0.40 m depth has four times the gauge pressure (ρgh) compared to Point R at 0.10 m depth, regardless of the oil's specific density. The absolute pressure includes atmospheric pressure P₀ at both points, but the pressure difference depends only on the depth difference. Choice D incorrectly implies that oil's lower density compared to water affects which point has higher pressure, when depth alone determines the ranking. For any fluid, deeper points have higher pressure following the same P = P₀ + ρgh relationship.
A crate is pulled across a floor, but only the downward normal force contributes to pressure. In case A the crate's contact area is $0.50\,\text{m}^2$ ; in case B it is $0.25\,\text{m}^2$ . The normal force is the same. Pressure is due to contact force. Which case has greater pressure?
Answer: Case B, because the same normal force is distributed over less area This question tests understanding of pressure as force per unit area. Pressure is calculated as P = F/A, where F is specifically the normal force (perpendicular to the surface) and A is the contact area. Since the normal force is the same in both cases but Case B has half the contact area (0.25 m²) compared to Case A (0.50 m²), Case B produces twice the pressure. The horizontal friction force from pulling does not contribute to vertical pressure. Choice D incorrectly suggests friction affects pressure, when only the perpendicular normal force matters. For pressure calculations, always identify which force component is perpendicular to the surface.
In a freshwater pool, pressure is due to fluid depth. Point $X$ is $1.5\,\text{m}$ below the surface and point $Y$ is $0.5\,\text{m}$ below. Which is correct?
Answer: $p_X>p_Y$ because the deeper point has greater pressure. This question tests understanding of pressure variation with depth in fluids. In static fluids, pressure increases with depth according to P = P₀ + ρgh. Point X at 1.5 m depth has greater pressure than point Y at 0.5 m depth because X has more water weight above it. The pressure difference is ρg(1.5 - 0.5) = ρg(1.0 m). Choice A incorrectly reverses this relationship, perhaps misunderstanding which point is deeper. When comparing fluid pressures, always identify which point is deeper below the surface, as deeper points have higher pressure.
A diver is in seawater. Point G is $2.0\,\text{m}$ below the surface and point H is $2.0\,\text{m}$ below the surface but horizontally $10\,\text{m}$ away. Pressure is due to fluid depth. Which point has greater water pressure?
Answer: They are equal, because both points are at the same depth This question assesses hydrostatic pressure, focusing on its dependence on vertical depth rather than horizontal position. In fluids, pressure increases with depth h as P = ρgh + P0, but is independent of horizontal distance. Points G and H are both at 2.0 m depth, so they have equal pressure despite the 10 m horizontal separation. The pressures are the same because only vertical depth matters. Choice B is a distractor that incorrectly claims pressure increases with horizontal distance, which is not true in static fluids. A transferable strategy is to ignore horizontal positions and base comparisons solely on vertical depths from the surface.
A hydraulic jack has a small piston of area $2.0\times10^{-4}\,\text{m}^2$ and a large piston of area $8.0\times10^{-3}\,\text{m}^2$ . A downward force of $50\,\text{N}$ is applied to the small piston. Pressure is due to contact force over area. Which statement about pressure in the fluid is correct?
Answer: Pressure is the same throughout the connected fluid at the same height. This question assesses pressure transmission in fluids for AP Physics 1, using contact force over area. Pressure is force per area, and in a confined, incompressible fluid, it is transmitted equally throughout at the same height. The applied force on the small piston creates a pressure that is the same under both pistons, per Pascal's principle. Despite different areas, the fluid pressure remains uniform. Choice A distracts by suggesting larger area means greater pressure, but pressure is independent of area in connected fluids. A transferable strategy is to apply Pascal's principle for equal pressures in hydraulic systems at equal heights.
A diver is at rest in freshwater. Point $C$ is $1.0\,\text{m}$ below the surface and point $D$ is $1.0\,\text{m}$ below the surface but near a slanted wall. Pressure is due to fluid depth. Compare pressures at $C$ and $D$ .
Answer: $P_C = P_D$ because they are at the same depth. This question assesses hydrostatic pressure in AP Physics 1, emphasizing its independence from container shape at the same depth. Pressure in a fluid increases with depth because of the cumulative weight of fluid layers above. At the same depth in a static fluid, pressure is equal regardless of nearby walls or shapes. Points C and D are both 1.0 m deep, so their pressures are identical. Choice A distracts by suggesting walls affect pressure, but hydrostatic pressure depends only on depth, density, and gravity. A transferable strategy is to focus on depth rather than container geometry when evaluating fluid pressure.
Two identical beakers are filled with the same liquid to the same height. One beaker is wide; the other is narrow. Point $E$ is $0.30\,\text{m}$ below the surface in the wide beaker and point $F$ is $0.30\,\text{m}$ below the surface in the narrow beaker. Pressure is due to fluid depth. Compare $P_E$ and $P_F$ .
Answer: $P_E = P_F$ because depth and fluid are the same. This question assesses hydrostatic pressure in AP Physics 1, based on fluid depth. Pressure increases with depth in a fluid due to the weight of the fluid column above, independent of container width. At the same depth in the same fluid, pressures are equal regardless of beaker shape. Points E and F are both 0.30 m deep, so $P_E$ equals $P_F$ . Choice A is a distractor, wrongly assuming more liquid in a wide beaker affects pressure, but only depth matters. A transferable strategy is to ignore container volume and focus on depth for pressure comparisons in static fluids.
A U-tube contains water open to air on both sides. Point $J$ on the left side and point $K$ on the right side are at the same vertical level within the water. Pressure is due to fluid depth. How do $P_J$ and $P_K$ compare?
Answer: $P_J = P_K$ because they are at the same depth in the same fluid. This question assesses hydrostatic pressure in AP Physics 1, depending on fluid depth. Pressure in a fluid increases with depth below the surface due to the weight of fluid above. In an open U-tube with equal atmospheric pressure on both sides, water levels are equal, so points at the same vertical level are at equal depths. Thus, $P_J$ equals $P_K$ . Choice A is a distractor, incorrectly linking pressure to tube width, but only depth matters. A transferable strategy is to confirm equal depths from surfaces for pressure equality in connected fluid systems.
A sealed container holds oil at rest. Point $C$ is $0.50\,\text{m}$ below the oil surface and point $D$ is $0.20\,\text{m}$ below; pressure is due to fluid depth. Which is greater?
Answer: $P_C>P_D$ because $C$ is deeper This question tests understanding of pressure in static fluids. In any fluid at rest, pressure increases with depth below the surface according to P = P_surface + ρgh. Point C at 0.50 m depth experiences greater pressure than point D at 0.20 m depth because it has more fluid weight above it. The pressure difference is ΔP = ρg(0.50 - 0.20) = 0.30ρg. Whether the container is sealed affects the surface pressure but doesn't change the fact that pressure increases with depth. Choice B incorrectly assumes sealing eliminates depth dependence. Remember that fluid pressure always increases with depth below the free surface, regardless of container shape or whether it's sealed.
In a column of water at rest, pressure is due to fluid depth. Point $M$ is $0.20\,\text{m}$ deeper than point $N$ . Which statement is correct?
Answer: $p_M>p_N$ because deeper points have more fluid above them. This question tests understanding of pressure variation with depth in fluids. In any static fluid, pressure increases with depth following P = P₀ + ρgh. Since point M is 0.20 m deeper than point N, M experiences greater pressure due to the additional weight of water above it. The pressure difference equals ρg(0.20 m), where ρ is water density and g is gravitational acceleration. Choice B incorrectly suggests pressure decreases with depth, which violates basic fluid statics principles. When analyzing fluid pressure, remember that pressure always increases as you go deeper, regardless of the fluid type or container.

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