ScienceMs. Curd

Force Definition: A push or a pull; something that

changes the motion of an objectUse forces all dayTo pick up backpacks Open and close doors

Different types of forceContact force: object pushes or pulls another

by touching itGravity: force of attraction between two

masses○ Larger mass=larger pull

Friction: force that resists motion between two surfaces that are pressed together

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

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 directionfor every action there is an equal and opposite

reaction

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

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

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

Collision

Definition: situation in which two objects in close contact exchange energy and momentumRear ended: car behind you bumps

you and transfers some of its momentum to your car

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 carTHEREFORE the total momentum of the

two cars has not changed (same as it was before the collision)

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?