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FORCE. Chapter 10 Text. Force. A push or a pull in a certain direction SI Unit = Newton (N). Combining Forces. The combination of all forces acting on an object is the Net Force. When forces act in the SAME DIRECTION = ADDITION. When forces act in the OPPOSITE DIRECTION = SUBTRACTION.
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FORCE Chapter 10 Text
Force • A push or a pull in a certain direction • SI Unit = Newton (N)
Combining Forces • The combination of all forces acting on an object is the Net Force.
Unbalanced forces • cause a change in the object’s motion.
Friction and Gravity • Friction – the force that two surfaces exert on each other when they rub
Types of Friction • 1. Static Friction • 2. Sliding Friction • 3. Rolling Friction • 4. Fluid Friction
Static Friction • Friction that acts on objects that are NOT moving
Sliding Friction • Occurs when two surfaces slide over each other
Rolling Friction • Occurs when an object rolls across a surface
Fluid Friction • Occurs when solid objects moves through fluids such as water, oil, or air
Friction depends on two factors: • 1. How hard the surfaces push together
Gravity • A force that pulls objects toward each other
2 Factors Affecting Gravity • 1. Distance • 2. Mass
Mass • The amount of matter in an object
Mass vs. Weight Mass is Constant because of the amount of matter does not change
The force of gravity on a person or object at the surface of a planet is known as weight.
Weight varies with the strength of the gravitational force, mass does not.
Gravity and Motion • Free fall – when the only force acting on a falling object is gravity
Acceleration due to gravity is • 9.8 m/s/s
All objects in free fall accelerate at the SAME rate regardless of their masses
Air Resistance • Falling objects with a greater surface area experience more air resistance.
Terminal Velocity • Reached when the force of air resistance equals the weight of the object
Newton’s 1st Law • an object at rest will remain at rest, an object in motion will stay in motion UNLESS acted upon by another force.
Inertia • Resistance to a change in motion • Newton’s 1st Law
Inertia depends on mass, the greater the mass the greater the inertia
Newton’s 2nd Law • Force = mass x acc.
End Unit for Acceleration • kg•m/s/s • Kg•m/s2 • Newton
Calculating: Calculate the slope of the graph. What does the slope tell you about the object’s motion?
The slope is 9.8. The speed increases by 9.8 m/s each second.
A speedboat pulls a 55-kg water-skier. The force causes the skier to accelerate at 2.0 m/s2. Calculate the force that causes this acceleration.
Fnet = mXa= 55 kg X 2.0 m/s2 • F = 110 kg • m/s2 • F = 110 N
What is the net force on a 1,000-kg object accelerating at 3 m/s2?