What is gravity?

A force that only planets and stars can produce A universal attractive force between any two objects with mass The force that makes objects fall when they are released A magnetic force between large objects

Newton's Law of Universal Gravitation states that the gravitational force between two objects depends on which two things?

The size (volume) of the objects and their temperature The masses of both objects and the distance between them Only the mass of the larger object and its speed The colour of the objects and their density

You double the distance between two objects. How does the gravitational force between them change?

It halves It stays the same — distance doesn't affect gravity It decreases to one quarter of its original value It doubles, because the objects are further apart

Newton realised that the force making an apple fall and the force keeping the Moon in orbit are the same force. Why was this a revolutionary idea?

It showed that apples and moons have the same mass It unified 'earthly' physics and 'heavenly' physics under one law — previously they were thought to be completely separate It proved that the Moon is made of the same material as apples It explained why apples always fall and moons always orbit in circles

Gravity is the weakest of the four fundamental forces, yet it dominates the universe on the largest scales. Why?

Because planets have no electric charge so only gravity can act on them It has infinite range and is always attractive — it never cancels out, so it accumulates over cosmic distances and masses Gravity becomes stronger over large distances unlike other forces Because gravity travels faster than other forces

Earth's gravitational field near the surface gives objects an acceleration of approximately 9.8 m/s² downward. What does this tell us?

Heavier objects fall faster because gravity acts more strongly on them Every second, a falling object's downward speed increases by 9.8 m/s, regardless of its mass Objects only accelerate at 9.8 m/s² if they weigh exactly 1 kg 9.8 m/s² is the speed at which all objects fall, not the acceleration

Does gravity act in space, far from any planet or star?

No — space is a vacuum so gravity cannot travel through it Only within our solar system — beyond that space has no gravity Yes — gravity has infinite range, though it weakens with distance Only if there are two or more planets nearby

Two objects, A (mass 2 kg) and B (mass 8 kg), are the same distance apart. Compared to the force on A from B, the force on B from A is:

Four times larger — B is four times more massive Four times smaller — B is harder to accelerate Equal — Newton's Third Law means gravitational forces are always paired and equal Zero — only the larger object experiences gravitational force

What is a gravitational field?

The surface of a planet where gravity is strongest The path that objects follow when gravity acts on them A region of space in which a mass experiences a gravitational force The force per square metre pressing on a planet's surface

General Relativity (Einstein's later theory) describes gravity differently from Newton. Which statement best describes Einstein's view?

Gravity is an electromagnetic force that acts between large masses Gravity is a repulsive force at very large distances Massive objects curve spacetime, and other objects follow curved paths through that warped spacetime Gravity is an illusion — objects only appear to be attracted because of their motion