๐ Newton’s second law
Newton’s first law explains that objects at quiescence (at rest) and objects in motion remain in their state unless they are affected by force. How do find what exactly force is needed for this to happen? The answer is given in Newton’s second law.
Newton’s second law states that an object changes its speed and direction due to the action of force. It also says that the mass of the object resists changes in its speed and direction. The greater the mass of an object is, the more it will resist this force and change. In other words, to change the direction of movement of an object with a larger mass will require more force.
What does this mean?
What is easier for you – to push an empty cart or a cart in which your friend rides? Correct! The lighter cart is easier to be pushed. You will need more force to push the cart with your friend in it, which is heavier than the empty one.
All this we mentioned above, can be written with a mathematical formula:
F = m . a ,
where
F – force, m – mass, a – acceleration
What does the formula say?
That the force is equal to the mass of the body multiplied by its acceleration. This means that the required force depends on body weight (mass) and its acceleration. The heavier it is, the more force will be needed, and also, the greater the acceleration of the body, the more force will be needed to apply it to change the acceleration.
What is acceleration?
This is any change in the speed and direction of motion of an object.
We observed that acceleration is the increase of speed in our daily things. And in physics, acceleration is EVERY CHANGE in speed and direction, whether it’s increasing or decreasing speed. Therefore, even slowing down or turning is an acceleration. Sounds amazing but it is a fact.
Every kind of acceleration requires force. For example, when you drive your child’s electric car and want to stop it, you press the brake pedal. Pressing the pedal puts pressure on the pedal. The force with which you press the brake pedal is exactly the force needed to change the acceleration (in this case to stop the car).
Another example: When you ride a bike and want to make a turn you also need to apply force on the handlebar on the bike. This is a lateral force that you apply to the handlebars of the bike, thus making it makes a turn.
Imagine now that you play with your friend and they drop a small plastic ball and a big oval stone on the same slope. Which will be easier to catch at the end of the slope? Yes – the plastic ball, because it is lighter and you will need to apply less force to stop and catch it. While the big stone is heavier and you would not be able to stop it and even it could knock you down.
Newton’s second law also explains why larger cars are safer than smaller ones. For example, if a truck and a car collide on the road, which vehicle will have more traces of the collision? Yes – the car will be much more crushed than the truck. Because you remember the mass of the object resists changes in its speed and direction, so bigger mass makes bigger resistance.
๐ฌ Observation: Inertia and mass – how to identify and observe it – click here.
Newton’s first law – see what it says.
Newton’s third law – check what it describes.