Physics - Term 2 - Week 5

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 introduces the concept of inertia. The second law quantifies the relationship between force, mass, and acceleration, expressed by the formula F = ma, where F is the net force, m is the mass, and a is the acceleration. The third law states that for every action, there is an equal and opposite reaction, highlighting the interaction between two objects.

Consider a scenario where a 5 kg object is pushed with a force of 20 N to the right and experiences a frictional force of 5 N to the left. To find the net force, we subtract the frictional force from the applied force: Net Force = 20 N - 5 N = 15 N to the right. This example illustrates how to calculate net force when multiple forces act on an object.

Let's work through a problem together. A car with a mass of 1,000 kg accelerates at 2 m/s². Using the formula F = ma, we can calculate the force. Here, F = 1,000 kg * 2 m/s² = 2,000 N. Now, try to determine the force if the car accelerates at 3 m/s² instead, keeping the mass the same.

For your independent practice, solve the following problems: 1) A 10 kg box is pushed with a force of 50 N. What is the acceleration of the box? 2) If the same box experiences a frictional force of 10 N, what is the new acceleration? Show all your calculations and reasoning.

• The relationship between force and mass.
• The concept of inertia.
• The action-reaction principle.
• The effect of gravity.

Answer: The concept of inertia.

Newton's first law describes how objects behave in the absence of net external forces, emphasizing the concept of inertia.

• F = mv
• F = ma
• F = m/a
• F = m + a

Answer: F = ma

The formula F = ma expresses the relationship between force, mass, and acceleration.

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

Newton's third law highlights the interaction between two objects, where forces are always mutual.

• 10 N
• 7 N
• 2 N
• 5 N

Answer: 10 N

Using F = ma, the force is calculated as 2 kg * 5 m/s² = 10 N.

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

Inertia is a property of matter that describes how much an object resists acceleration.

• A ball rolling down a hill.
• A rocket launching into space.
• A car stopping at a red light.
• A person pushing a stationary car.

Answer: A rocket launching into space.

A rocket's launch involves the application of force to overcome inertia and accelerate.

• Acceleration increases.
• Acceleration decreases.
• Acceleration remains the same.