Motion A change in the position of an object Caused by force (a push or pull)
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Transcript of Motion A change in the position of an object Caused by force (a push or pull)
Motion
• A change in the position of an object
• Caused by force (a push or pull)
Force• A push or pull on an object• Measured in units called newtons (N)• Measured with a spring scale• Forces act in pairs
Types of Force:– Gravity– Electric– Magnetic– Friction– Centripetal– Normal
Balanced Forces
• When all the forces acting on an object are equal (net force is zero)
• Balanced forces do not cause a change in motion.
• Balanced forces can change the physical properties of an object without changing its motion.
• In your notes, describe an example of a balanced force.
How Can Balanced Forces Affect Objects?
• Cause the shape of an object to change without changing its motion
• Cause an object at rest to stay at rest or an object in motion to stay in motion (inertia)
• Cause an object moving at a constant speed to continue at a constant speed
• In your notes, describe an example of a balanced force affecting an object.
Inertia
• An object at rest will remain at rest until acted upon by an unbalanced force.
• An object in motion will remain in motion until acted upon by an unbalanced force.
• When all forces acting on an object are equal (balanced)
Unbalanced Forces
• When all the forces acting on an object are not equal
• The forces can be in the same direction or in opposite directions.
• Unbalanced forces cause a change in motion.
• In your notes, describe an example of an unbalanced force.
How Can Unbalanced Forces Affect Objects?
• Acceleration is caused by unbalanced forces:– slow down– speed up– stop – start – change direction– change shape
• In your notes, describe an example of an unbalanced force affecting an object.
Net Force
• The total of all forces acting on an object:
– Forces in the same direction are added.• The object will move in the direction of the force.
– Forces in opposite directions are subtracted.• An object will move in the direction of the greater
force.
Calculating Net Force
30 N 10 N
A child was playing with a jack in the box. The lid pushed down with 10 N of force, while the spring pushed up with 30 N of force. What is the net force applied by the spring?
http://commons.wikimedia.org/wiki/File:Jack-in-the-box.jpg
Check Your Answer
30 N 10 N
A child was playing with a jack in the box. The lid pushed down with 10 N of force, while the spring pushed up with 30 N of force. What is the net force applied by the spring?
30 N up - 10 N down = 20 N up
http://commons.wikimedia.org/wiki/File:Jack-in-the-box.jpg
Calculating Net Force
30 N 50 N
Two competitors are playing tug of war. What is the net force? Which direction will the rope accelerate?
Tug of War Game
Check Your Answer
30 N 50 N
Two competitors are playing tug of war. What is the net force? Which direction will the rope accelerate?
50 N to the right – 30 N to the left = 20 N to the right
Tug of War Game
• Draw the box and label the forces.50N 50N
Copy the sentences and fill in the blanks.
1. The forces are ______________.2. The net force is _____________.3. The object will accelerate ______________.
Thursday Warm upNovember 13, 2014
Force and Motion Video
Visual vocabulary
Force and Motion
Aaron Harrell9-14-2010
Force
PUSH
Motion
Speed
Velocity
&
Acceleration
Balanced Forces
Unbalanced Forces
Friday Warm upNovember 14, 2014
• Find the formula for Force on your formula chart and write it down.
• Calculate the force (N) of an object if the mass is 25kg and the acceleration is 2.3 m/s².
Objects affected by unbalanced forces move like…
Objects affected by balanced forces move like…
Mass and Weight• Mass is the amount of stuff (matter) in an object.
– The mass of an object will remain the same anywhere in the universe.– Mass is measured in grams or kilograms.
• Weight is the mass (kg) of an object multiplied by the acceleration of gravity (9.8 m/s2).– The weight of an object depends on the gravitational pull of the
location in the universe.– The gravitational pull on the Moon is only 1/6 of Earth’s gravitational
pull.– Weight is measured in newtons (N).
Mass and Weight
Example: F=ma
A person with a mass of 25 kg x 9.8 m/s2 gravitational acceleration is equal to 245 N of weight force.
F= 25 kg x 9.8 m/s2
F = 245 N
The person exerts 245 N of force on the ground.If the person went to the Moon, they would only weigh 1/6 of 245 N.
Force Force (N) = mass (kg) x acceleration (m/s2)
F ÷
m x a
Force Acceleration (m/s2) = force (N) ÷ mass (kg)
F ÷
m x a
Force Mass (kg) = force (N) ÷ acceleration (m/s2)
F ÷
m x a
PracticeThe acceleration of a sprinter is 10 m/s2. The force exertedon the starting blocks is 650 N. What is the mass of thesprinter?
Force = Mass = Acceleration =
Check Your AnswerThe acceleration of a sprinter is 10 m/s2. The force exerted on the starting blocks is 650 N. What is the mass of the sprinter?
Force = 650 N Mass = 65 kg Acceleration = 10 m/s2
Mass = force ÷ acceleration
Mass = 650 ÷ 10 Mass = 65
PracticeA 56 kg cart is accelerating at 15 m/s2. Calculate the forceexerted on the cart?
Force = Mass = Acceleration =
Check Your AnswerA 56 kg cart is accelerating at 15 m/s2. Calculate the forceexerted on the cart?
Force = 840 N Mass = 56 kg Acceleration = 15 m/s2
Force (N) = mass (kg) x acceleration (m/s2) Force = 56 x 15 Force = 840
PracticeA boat is pulling a 54 kg wake boarder. The force causing the
acceleration is 108N. Calculate the acceleration of the wake boarder.
Force = Mass = Acceleration =
Check Your AnswerA boat is pulling a 54 kg wake boarder. The force causing the
acceleration is 108N. Calculate the acceleration of the wake boarder.
Force = 108 N Mass = 54 kg Acceleration = 2 m/s2