Forces. What Is a Force? Force- a push or a pull that acts on an object o Can cause a resting object...
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Transcript of Forces. What Is a Force? Force- a push or a pull that acts on an object o Can cause a resting object...
Forces
What Is a Force?
• Force- a push or a pull that acts on an objecto Can cause a resting object to move, or it can
accelerate a moving object • Forces are measured in Newtons (N)• One newton is the forces that causes 1 kg mass to
accelerate at a rate of 1 meter per second each second
o 1 N = 1 kg*m/s2
Representing Force
• Forces can’t be seen, but their effects can. So we have come up with a way to represent forces
Forces can be combined
• Forces in the same direction add together
• Forces in opposite directions subtract from one another
• The net force is the overall force acting on an object after the forces are combined
Balanced and Unbalanced Forces
• When forces on an object are balanced, the net force in zero and there is no change in the object’s motion
• When an unbalanced force acts on an object, the object accelerates
Friction
• A force that opposes the motion of objects that touch as they move past each other
• 4 main types of friction:1.) static friction2.) sliding friction3.) Rolling friction4.) fluid friction
Static Friction
• Acts on object that are not moving- Always acts in the direction opposite to that of
the applied force- You experience static friction every time you
take a step
Sliding Friction
• Force that opposes the direction of motion of an object as it slides over a surface
- Less than static friction. Therefore, less force is needed to keep an object moving than to start it moving
Rolling Friction
• Friction force that acts on rolling objects- 100 to 1000 times less than the force of static
or sliding friction- Helps explain why professional movers use
wheeled dollies to move heavy objects
Fluid Friction
• Opposes the motion of an object through a fluid- Examples can be seen on a submarine moving
through water or an airplane flying through air - You can feel fluid friction when stirring thick cake
batter- Increases as the speed of the object moving
through the fluid increases- Fluid friction acting on an object moving through
the air is known as air resistance
Gravity
• Force that acts between any 2 masses-attractive force—pulls objects together-does not require objects to be in contact-can act over long distances-Earth’s gravity acts downward toward the center of Earth
Falling Objects
• Gravity causes objects to accelerate downward, whereas air resistance acts in the direction opposite to the motion and reduces acceleration
Falling objects
• As objects fall to the ground, they accelerate and gain speed
• Terminal velocity is the constant velocity of a falling object when the force air resistance equals the force of gravity
-the doesn’t mean the objects stop in mid air…it just means it doesn’t accelerate anymore• Mass does NOT matter, all objects fall at the
same rate
Projectile Motion
• The motion of a falling object (projectile) after it is given an initial forward velocity.
- Air resistance and gravity are the only forces acting on a projectile