1. Science Ms. Curd

2. Force  Definition: A push or a pull; something that changes the motion of an object Use forces all day To pick up backpacks Open and close doors  Different types of force Contact force: object pushes or pulls another by touching it Gravity: force of attraction between two masses ○ Larger mass=larger pull Friction: force that resists motion between two surfaces that are pressed together

3. Net Force  Definition: the overall force acting on an object when all the forces are combined  If it is zero - the forces are balanced; same effect as no force at all, no change in motion  Unbalanced forces change the motion of the object

4. Newton’s 3 Laws of Motion  Sir Isaac Newton  First Law: objects at rest remain at rest, and objects in motion remain in motion unless acted upon by an unbalanced force  Second Law: acceleration of an object increases with increased force and decreases with increased mass  Third law: Every time one object exerts a force on another object, the second object exerts a force that is equal in size and opposite in direction for every action there is an equal and opposite reaction

5. Inertia  Definition: resistance of an object to a change in the speed or direction of its motion  The more mass there is the more inertia there is

6. Formula for Force  Force equals Mass times Acceleration  Force = Mass * Acceleration  F = m * a or F = ma  Standard unit is the Newton – amount of force it takes to accelerate 1 kg of mass 1 m/s/s  What force do you need to accelerate a 10 kg shopping cart 3 m/s/s? ○ F = ma ○ F = 10 kg * 3 m/s/s ○ F = 30 kg * m/s/s ○ F = 30 N

7. Momentum  Definition: A measure of mass in motion More mass equals more momentum at the same speed Two objects with the same mass can have different momentums if they have different speeds ○ Which does more damage? A wrecking ball with lots of momentum or one with little momentum? The one with more momentum, greater speed

8. Collision  Definition: situation in which two objects in close contact exchange energy and momentum Rear ended: car behind you bumps you and transfers some of its momentum to your car

9. Conservation of Momentum  Definition: the total momentum of a system of objects does not change, as long as no outside forces are acting on that system  If two cars are in collision: One car may lose momentum, but it is gained by the other car THEREFORE the total momentum of the two cars has not changed (same as it was before the collision)

10. Formula Practice  On a separate sheet of paper: Solve using the Force formula (F = ma) 1. If a 5 kg ball is accelerating 1.2 m/s/s, what is the force on it? 2. A girl pulls a wheeled backpack with a force of 3 N. If the backpack has a mass of 6 kg, what is its acceleration? 3. A boy pushes a shopping cart with a force of 10 N, and the cart accelerates 2 m/s/s. What is the mass of the cart? 4. A person on a scooter is accelerating 2 m/s/s. If the person has a mass of 50 kg, how much force is acting on that person? 5. If a 10 N force accelerates an object 5 m/s/s, what is the mass of the object?