Physics - Term 3 - Week 2

Newton's first law states that an object at rest stays at rest, and an object in motion stays in motion unless acted upon by a net external force. This principle emphasizes the concept of inertia. The second law of motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass, expressed mathematically as F = ma. Finally, the third law states that for every action, there is an equal and opposite reaction, highlighting the interaction between forces.

Consider a scenario where two forces are acting on an object: a 10 N force to the right and a 5 N force to the left. To find the net force, we subtract the leftward force from the rightward force: Net Force = 10 N - 5 N = 5 N to the right. This example illustrates how to determine the net force when multiple forces are acting on an object.

In pairs, students will observe a scenario in the classroom, such as a book resting on a table. They will identify the forces acting on the book, including gravitational force pulling it down and the normal force from the table pushing it up. Students will discuss how these forces balance each other, resulting in no net force and thus no motion.

Students will complete a worksheet where they are given various scenarios involving different masses and forces. They will calculate the acceleration of objects using the formula a = F/m. For example, if a 20 N force is applied to a 4 kg object, the acceleration can be calculated as a = 20 N / 4 kg = 5 m/s².

• The relationship between force and mass
• The concept of inertia
• The action-reaction principle
• The acceleration of an object

Answer: The concept of inertia

Newton's first law describes how objects behave when no net external forces act on them, which is essentially inertia.

• 5 m/s²
• 10 m/s²
• 15 m/s²
• 20 m/s²

Answer: 5 m/s²

Using F = ma, acceleration a = F/m = 15 N / 3 kg = 5 m/s².

Answer: For every action, there is an equal and opposite reaction.

This law explains how forces always occur in pairs.

• A ball rolling on the ground
• A rocket launching into space
• A car at rest
• A person jumping off a diving board

Answer: A rocket launching into space

The rocket's acceleration is due to the net force produced by the engines, illustrating F = ma.

Answer: Inertia is the tendency of an object to resist changes in its state of motion.

Inertia is directly related to mass; more massive objects have greater inertia.

• It speeds up
• It slows down
• It continues moving at a constant velocity
• It stops

Answer: It continues moving at a constant velocity

According to Newton's first law, an object in motion will remain in motion unless acted upon by a net external force.

• Gravity
• Friction
• Tension
• Normal force