Gravity and Forces

Grade 5 · Science · Study Guide

Explore how forces including gravity affect the motion of objects and shape our everyday experiences.

A force is a push or pull that can change the motion of an object. Forces have two characteristics: magnitude (strength) and direction. When forces on an object are balanced, the object stays still or continues moving at the same speed and direction. When forces are unbalanced, the object accelerates (changes speed or direction).

Gravity is the force of attraction between any two objects that have mass. The more mass an object has and the closer two objects are, the stronger the gravitational force between them. Earth's gravity pulls all objects toward its center with an acceleration of about 9.8 meters per second squared.

Weight is the measurement of the gravitational force on an object. Mass is the amount of matter in an object — mass stays the same everywhere, but weight changes depending on gravity. On the Moon (which has weaker gravity), you would weigh less but have the same mass.

Friction is a force that opposes motion between two surfaces in contact. Air resistance is friction between a moving object and air. Other common forces include applied forces (a push or pull you apply), tension (pulling force through a rope), and the normal force (a surface pushing back on an object resting on it).

Key terms

Force
A push or pull on an object; measured in Newtons (N) and has both magnitude and direction.
Gravity
An attractive force between objects with mass; pulls objects toward each other.
Mass
The amount of matter in an object; remains constant regardless of location.
Weight
The force of gravity acting on an object's mass; changes based on gravitational strength of the location.
Friction
A force that opposes the motion of objects sliding against each other.
Balanced Forces
When all forces on an object cancel out and the net force is zero, resulting in no change in motion.

Flashcards

Newton (N)
The unit used to measure force. Named after Sir Isaac Newton who described the laws of motion and gravity.
Gravity on Earth
Earth's gravity accelerates all falling objects at about 9.8 m/s² (ignoring air resistance).
Unbalanced Forces
When net force is NOT zero, the object accelerates — it changes speed or direction of motion.
Air Resistance
A type of friction that acts on objects moving through air; slows them down.
Normal Force
The force a surface exerts perpendicular to an object resting on it — it pushes back against gravity.
Isaac Newton
Scientist who formulated the laws of motion and law of universal gravitation in the 17th century.

Questions

  1. What happens to an object when balanced forces act on it?

    1. It speeds up
    2. It slows down immediately
    3. It remains at rest or continues moving at the same speed and direction
    4. It moves in a circle
    Show answer

    Answer: It remains at rest or continues moving at the same speed and direction

    Balanced forces produce a net force of zero. According to Newton's first law, an object at rest stays at rest and an object in motion continues at the same velocity when forces are balanced.

  2. An astronaut on the Moon has less mass than on Earth because the Moon's gravity is weaker.

    Show answer

    Answer: False

    Mass is the amount of matter in an object and does NOT change based on location or gravity. The astronaut's weight (gravitational force) is less on the Moon, but mass is identical.

  3. The force that opposes motion between two surfaces in contact is called ________.

    Show answer

    Answer: friction

    Friction is the force that resists motion when two surfaces are in contact. It acts in the opposite direction of motion and can slow or stop moving objects.

  4. Which of the following would increase the gravitational force between two objects?

    1. Moving the objects farther apart
    2. Decreasing the mass of both objects
    3. Increasing the mass of both objects and moving them closer
    4. Reducing friction between them
    Show answer

    Answer: Increasing the mass of both objects and moving them closer

    Gravitational force increases with greater mass and decreases with greater distance. Increasing both objects' masses AND bringing them closer together maximizes gravitational attraction.

  5. Weight and mass measure the same thing and are interchangeable terms.

    Show answer

    Answer: False

    Mass is the amount of matter in an object (constant everywhere). Weight is the force of gravity on that mass (varies by location). They are related but measure different things.

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