1. Force

2. A little History Isaac Newton was an English physicist/astronomer among other things and made a number of significant advances in the study of the world around us and in space. He was allegedly struck on the head by an apple falling from a tree which eventually led to his developing his three laws of motion now known as: Newton’s Laws of Motion

3. Newton’s First Law Newton’s First Law of Motion deals with the effects of balanced and unbalanced forces. (Newton’s Law’s are one of the main reasons that the units for force are in Newtons) Wording of Newton’s First Law: An object in motion will stay in motion and an object at rest will stay at rest unless an unbalanced force is acted upon it -- often called the law of inertiainertia

4. Inertia Inertia is the tendency of objects to resist any change in motion. The amount of inertia that an object has is directly related to its mass - the more massive an object is, the more inertia an object has

5. Inertia Think about it like this: Which is harder to get rolling, a train or a Tonka truck? OR Which would you rather try to stop, a train moving at 5 km/hr or a Tonka truck moving at 5 km/hr?

6. More Examples Of Inertia Example 1: When you’re riding in a car, and the car slams on its brakes, your body keeps going forward until a force acts upon it. Hopefully, that force is the seat belt. Example 2: Demonstrations in the lab today with coins. Even though the other coins/index cards moved, the coin stayed still because no force was acted upon it

7. Basically, an object will move at constant velocity unless an unbalanced force is acted upon itunbalanced force **remember that being stopped (a velocity of 0 m/s) is still a constant velocity!!!** Newton’s First Law

8. What is this Force thing? Force – the push or pull of one object on another Force is a vector quantity, therefore, whenever calculating force, you must give: -- an amount -- a unit -- a direction We very often represent the direction of force with arrows.

9. A glimpse of things to come… Force is a measure of how strong the push or pull is on one object by another. Think about if you were pushing on objects in the real world. If you push with all your might against a small box full of feathers, you would get it moving faster than if you pushed with all your might against a small box full of bricks. Mass, as you will see, is a factor to consider when we talk about forces.

10. Units for Force Therefore, while mass is obviously a factor, speed and acceleration also play a role in calculating force When reporting force, we use the units of Newtons (N) 1 N = 1 kg m/s 2 -- the units for Newtons are derived from the formula for force, which we will look at later -- YOU MUST ALWAYS remember that mass must be in kilograms (kg) when calculating force The unit Newton, of course, is named for the famous scientist Sir Isaac Newton, who spent much of his time investigating forces

11. Types of Forces There are many different types of forces, including: -- Frictional force (how strong friction is) -- Gravitational force (weight) -- Torque (perpendicular force) No matter what type of force you are talking about acting on an object, that force is either balanced or unbalanced

12. The elephant has more inertia because it has more mass. The velocity of an object does not affect its inertia Questions 1.According to Newton, what do objects want to do? 2.Which has more inertia, a walking elephant or an eighth grader flying down Broad Street on a bike? Answer Maintain their motion; stationary objects will continue to not move and objects in motion will keep their same velocity until acted upon by a net force

13. Questions 3. What is a force? 4. What is the unit for force and where does it come from? The unit is the Newton (N) and it is made up of kilograms times meters per second squared Answer A force is any push or pull one object exerts on another