CCEA GCSE Physics 1.2 Force Exam Questions

About CCEA GCSE Physics 1.2 Force

Force is a large Unit 1 topic in CCEA GCSE Physics. It covers resultant forces, friction, Newton's first and second laws, the difference between mass and weight, and how springs stretch according to Hooke's law. You also need pressure, moments, the Principle of Moments and how the centre of gravity affects stability. There are two prescribed practicals: extension of a spring and verifying the Principle of Moments. CCEA uses g = 10 N/kg throughout. The topic builds on 1.1 Motion and links to work done in 1.4. Examiners often set F = ma and moment calculations, ask for interpretation of a force-extension graph and test the conditions for equilibrium.

What you need to know

• Resultant force and Newton's first law Forces act in pairs and are measured in newtons. Add forces in the same direction and subtract opposite ones to find the resultant. If the resultant force is zero, an object stays at rest or keeps moving at a constant velocity.
• Newton's second law Resultant force = mass x acceleration, F = ma. A resultant force changes speed or direction. Friction opposes motion.
• Mass and weight Mass (kg) is the amount of matter and does not change. Weight is the force of gravity on a mass: W = mg, with g = 10 N/kg on Earth. All objects falling freely near the Earth accelerate at 10 m/s2 if air resistance is negligible.
• Hooke's law and the spring practical Force = spring constant x extension, F = ke, up to the limit of proportionality. Hang masses on a spring, measure the extension with a metre rule and plot force against extension; the gradient of the straight-line section is the spring constant in N/m (or N/cm).
• Pressure Pressure = force / area, P = F/A, in pascals (Pa), where 1 Pa = 1 N/m2. A small area gives a large pressure (knife edge, drawing pin); a large area gives a small pressure (snowshoes).
• Moments Moment = force x perpendicular distance from the pivot, in Nm. Principle of Moments: for a balanced object, the sum of clockwise moments equals the sum of anticlockwise moments. Verify it with a metre rule balanced on a pivot and masses hung on each side.
• Centre of gravity and stability The centre of gravity is the point where the whole weight appears to act. An object topples when its weight acts outside its base. A low centre of gravity and wide base increase stability.

Common mistakes in 1.2 Force

• Giving weight in kilograms. Weight is a force measured in newtons.
• Using the distance along a slanted bar rather than the perpendicular distance when calculating moments.
• Measuring the length of the spring instead of the extension. Extension = stretched length - original length.
• Saying that an object moving at constant speed must have a resultant force on it. At constant velocity the resultant force is zero.
• Forgetting to convert cm2 to m2 when calculating pressure in pascals.

Try three 1.2 Force exam-style questions