Formula & Theorem Quick Reference for Year 8 CIE Science | Year 8 CIE 科学：公式定理速查手册

📚 Formula & Theorem Quick Reference for Year 8 CIE Science | Year 8 CIE 科学：公式定理速查手册

This quick reference handbook summarises the essential formulas and theorems that Year 8 students need for CIE Science. Understanding these relationships is key to solving problems in physics, chemistry and biology. Use this guide to revise, practice rearranging equations, and apply concepts confidently in exams.

这本速查手册总结了 Year 8 CIE 科学考试所需的核心公式和定理。理解这些关系是解决物理、化学和生物问题的关键。用这份指南进行复习，练习公式变形，并在考试中自信地应用概念。

1. Speed | 速度

Speed measures how fast an object moves. It is calculated by dividing the distance travelled by the time taken.

速度衡量物体运动的快慢。通过移动的距离除以所用的时间来计算。

v = s / t

where v = speed (m/s), s = distance (m), t = time (s). The SI unit of speed is metres per second.

其中 v = 速度（米/秒），s = 距离（米），t = 时间（秒）。速度的国际单位是米每秒。

To find distance: s = v × t. To find time: t = s / v.

求距离：s = v × t。求时间：t = s / v。

---

2. Acceleration | 加速度

Acceleration is the rate of change of velocity. It can be positive (speeding up) or negative (slowing down, sometimes called deceleration).

加速度是速度变化的快慢。可以是正的（加速）或负的（减速，有时称为减速度）。

a = (v – u) / t

where a = acceleration (m/s²), v = final velocity (m/s), u = initial velocity (m/s), t = time (s).

其中 a = 加速度（米/秒²），v = 末速度（米/秒），u = 初速度（米/秒），t = 时间（秒）。

---

3. Density | 密度

Density describes how much mass is packed into a given volume. It helps identify materials and predict whether an object will float or sink.

密度描述单位体积内所含的质量。用于鉴别材料并预测物体的沉浮。

ρ = m / V

where ρ (rho) = density (kg/m³ or g/cm³), m = mass (kg or g), V = volume (m³ or cm³).

其中 ρ (rho) = 密度（千克/米³ 或 克/厘米³），m = 质量（千克或克），V = 体积（米³ 或 厘米³）。

Water has a density of 1 g/cm³. Objects with density greater than water sink; those with density less than water float.

水的密度为 1 g/cm³。密度大于水的物体会下沉；密度小于水的则会漂浮。

---

4. Hooke’s Law | 胡克定律

Hooke’s Law states that the extension of a spring is directly proportional to the force applied, provided the elastic limit is not exceeded.

胡克定律指出，在弹性限度内，弹簧的伸长量与所施加的力成正比。

F = k × x

where F = force (N), k = spring constant (N/m), x = extension (m). The spring constant measures stiffness.

其中 F = 力（牛顿），k = 弹簧常数（牛/米），x = 伸长量（米）。弹簧常数衡量弹簧的刚度。

---

5. Pressure | 压强

Pressure is the force acting per unit area. A sharp knife cuts better than a blunt one because the area is smaller, producing higher pressure.

压强是单位面积上所受的力。锋利的刀比钝刀切东西更容易，因为接触面积小，压强大。

P = F / A

where P = pressure (Pa or N/m²), F = force (N), A = area (m²).

其中 P = 压强（帕斯卡或牛/米²），F = 力（牛顿），A = 面积（米²）。

In liquids, pressure increases with depth and is given by: P = h × ρ × g (h = depth in m, ρ = liquid density in kg/m³, g = gravitational field strength, ~10 N/kg).

在液体中，压强随深度增加，公式为：P = h × ρ × g（h 为深度，米；ρ 为液体密度，千克/米³；g 约为 10 牛/千克）。

---

6. Moment of a Force | 力矩

Published by TutorHao | Year 8 Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）