Physics - Term 4 - Week 2

Newton's first law states that an object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity unless acted upon by a net external force. This law emphasizes the concept of inertia. The second law 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. 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 a box: a 10 N force to the right and a 5 N force to the left. To find the net force, we subtract the opposing forces: Net Force = 10 N - 5 N = 5 N to the right. This example illustrates how to determine the overall force acting on an object when multiple forces are present.

In pairs, students will observe their surroundings and list at least five examples of forces they can identify. For instance, they might note the force of gravity acting on a dropped ball or friction between a sliding book and a table. After compiling their lists, each pair will share their findings with the class, discussing how these forces affect motion.

Students will be given a worksheet with various scenarios where they need to 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, students will calculate the acceleration as follows: a = 20 N / 4 kg = 5 m/s². This exercise will reinforce their understanding of the relationship between force, mass, and acceleration.

• 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 emphasizes that an object will not change its state of motion unless acted upon by a net external force, which is the essence of inertia.

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

Answer: 5 m/s²

Using the formula a = F/m, we calculate acceleration as 15 N / 3 kg = 5 m/s².

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

This law explains that forces always occur in pairs; when one object exerts a force on another, the second object exerts a force of equal magnitude and opposite direction back on the first.

• A car accelerating on a highway
• A book sliding off a table
• A person pushing a shopping cart
• A ball rolling on grass

Answer: A book sliding off a table

Friction is the force that opposes the motion of an object, and it is evident when the book slides off the table.

Answer: Net Force = F1 + F2 + ... + Fn (considering direction)

Net force is the vector sum of all individual forces acting on an object, taking into account their directions.

• It accelerates
• It remains at rest or continues moving at constant velocity
• It stops immediately
• It changes direction

Answer: It remains at rest or continues moving at constant velocity

According to Newton's first law, an object will maintain its state of motion unless acted upon by a net external force.