Technical Science - Term 1 - Week 3

Newton's First Law, also known as the Law of Inertia, states that an object at rest will remain at rest, and an object in motion will continue in motion with the same speed and in the same direction unless acted upon by a net external force. This principle highlights the concept of inertia, which is the tendency of an object to resist changes in its state of motion.

Newton's Second Law quantifies the relationship between force, mass, and acceleration. It is expressed by the formula F = ma, where F is the net force applied to an object, m is the mass of the object, and a is the acceleration produced. This law indicates that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

Newton's Third Law states that for every action, there is an equal and opposite reaction. This means that forces always occur in pairs; when one object exerts a force on a second object, the second object exerts a force of equal magnitude and opposite direction on the first object. This principle is crucial in understanding interactions between objects.

Consider a 5 kg object being pushed with a net force of 20 N. To find the acceleration, we use the formula a = F/m. Substituting the values, we get a = 20 N / 5 kg = 4 m/s². This means the object will accelerate at 4 meters per second squared in the direction of the applied force.

When a swimmer pushes against the wall of a pool, they exert a force on the wall. According to Newton's Third Law, the wall exerts an equal and opposite force back on the swimmer. This reaction force propels the swimmer forward in the water, demonstrating the practical application of this law.

Let's work through a problem together. A car with a mass of 1,200 kg accelerates at 3 m/s². What is the net force acting on the car? Using F = ma, we calculate F = 1,200 kg * 3 m/s² = 3,600 N. Now, try to solve a similar problem with a different mass and acceleration.

Complete the following problems on your own: 1) A 10 kg box is pushed with a force of 50 N. What is its acceleration? 2) If a 2 kg ball is dropped, what is the force acting on it due to gravity? 3) Describe a real-life situation that illustrates Newton's Third Law. Write your answers and be prepared to discuss them in class.

• An object will accelerate if a force is applied.
• An object at rest will stay at rest unless acted upon.
• For every action, there is an equal and opposite reaction.
• Mass and acceleration are directly related.

Answer: An object at rest will stay at rest unless acted upon.

This statement reflects the principle of inertia, which is central to Newton's First Law.

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

Answer: F = ma

Newton's Second Law is defined by the equation F = ma, where F is force, m is mass, and a is acceleration.

• A car accelerating down a hill.
• A rocket launching into space.
• A ball rolling on the ground.
• A person pushing against a wall.

Answer: A person pushing against a wall.

This example illustrates the action-reaction pair described by Newton's Third Law.

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

Inertia is a key concept in Newton's First Law, highlighting how objects behave when no net force is acting on them.

• 3 m/s²
• 4 m/s²
• 2 m/s²
• 1 m/s²

Answer: 3 m/s²

Using F = ma, we find a = F/m = 12 N / 4 kg = 3 m/s².

Answer: A car accelerating when the driver presses the gas pedal.

This example shows how the force applied by the engine results in acceleration, as described by Newton's Second Law.