Gravitational Force
What force causes objects to fall toward the ground when released in the air?
Gravitational force (gravity)
Every magnet has two poles. What are they called?
North (N) pole and South (S) pole
What is friction? In one sentence, describe what it does to a moving object.
riction is a force that opposes motion — it slows down or stops a moving object
What is the difference between mass and weight?
Mass is the amount of matter in an object (measured in kg); weight is the gravitational force acting on the object (measured in Newtons)
What happens when the North pole of one magnet is placed near the South pole of another magnet?
The unlike poles attract each other
In Experiment 2, a heavier box needed more force to move than a lighter box. What conclusion can you draw about mass and friction?
The greater the mass of an object, the greater the friction between it and the surface
An astronaut weighs 800 N on Earth but only 130 N on the Moon. Her mass on Earth is 80 kg. What is her mass on the Moon?
80 kg — mass does not change with location, only weight does
A student tests an iron nail and a bar magnet with another magnet. Both are attracted to it. What extra test should the student do to find out which one is a magnet?
Test whether the object can repel one end of a known magnet — only a magnet can repel
A wooden block slides 30 cm on a smooth plank but only 20 cm on a rough plank released from the same height. Identify the independent variable and one controlled variable in this experiment.
Independent variable: type of surface (smooth vs rough). Controlled variable: any one of — height of release, mass of block, length of plank
A ball is thrown upward and follows a curved path before hitting the ground. Explain how gravitational force causes this curved path.
Gravitational force acts downward on the ball at all times, even while it is moving upward and sideways, continuously changing its direction and pulling it toward the ground
A junkyard crane uses an electromagnet to lift steel cars but cannot lift aluminium cans. Explain why, using what you know about magnetic materials.
Steel is a magnetic material and is attracted to magnets; aluminium is not a magnetic material so it is not attracted
A racing car designer wants to reduce friction between the tyres and the road as little as possible, while an engineer designing a car's brakes wants to maximise friction. Explain how each goal is achieved and why they conflict.
Reducing tyre friction: use smooth tyres or lubricants — but this reduces braking grip. Maximising brake friction: use rough brake pads pressed hard against the wheel — but this increases heat and wear. They conflict because friction is needed for braking but wastes energy in driving
For an aeroplane to take off, its lift force must overcome its weight. If the plane has a mass of 50 000 kg and weight of 500 000 N, what upward force must the engines produce at minimum, and why?
The lift force must be greater than 500 000 N (the weight) to accelerate the plane upward — if lift equals weight the plane stays level; it must exceed weight to rise
Two ring magnets are placed on a pole so that like poles face each other. The top magnet floats. As more magnets are added below, the gap between adjacent magnets decreases. Explain why the gaps get smaller toward the bottom.
The magnets lower down must support the weight of more magnets above them, so the repulsive magnetic force must be greater, meaning the magnets are pushed closer together to generate a stronger force
A student claims that polishing a surface always reduces friction. Evaluate this claim — is it always true? Use evidence to justify your answer.
Not always — polishing reduces friction between most surfaces because it removes bumps, letting surfaces slide more easily. However, very smooth surfaces can increase friction due to greater contact area (e.g. polished metal on metal). The claim is mostly correct but oversimplified