Download - Blue Cow- Recall F net = ma
![Page 1: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/1.jpg)
Blue Cow- Recall Fnet = ma
• A 1.2 × 103-kilogram automobile in motion strikes a 1.0 × 10-4-kilogram insect. As a result, the insect is accelerated at a rate of 1.0 × 102 m/s2. What is the magnitude of the force the insect exerts on the car?
a)1.0 × 10-2 Nb)1.2 × 10-2 Nc)1.0 × 101 Nd)1.2 × 103 N
![Page 2: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/2.jpg)
Objective
• Explore what causes motion ! Apply Newton’s laws of motion to the world around us.
![Page 3: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/3.jpg)
![Page 4: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/4.jpg)
Homework
• Castle Learning – Newton 1
• Possible Test Next Friday.
![Page 5: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/5.jpg)
Force
• Force is a vector quantity, therefore it has both magnitude and direction.
• The SI unit for force is the Newton.– The Newton is a derived unit where:
1N = 1kg•m/s2
– 1 Newton is the amount of force required to accelerate a 1 kg mass 1 m/s2.
![Page 6: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/6.jpg)
The System and Environment• The object of interest is called the
System.
• The area around the object is called the Environment.
Fg
FN
System
Environment
![Page 7: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/7.jpg)
Newton’s 2nd Law and Force vs. Acceleration
• How does acceleration relate to force?– As the force on an object increases, the rate
of acceleration will increase.
Acceleration
m1
m2
m2 > m1
Note: The slope of the line in a F vs. a graph will equal the mass of the object.The greater the slope, the greater the mass
![Page 8: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/8.jpg)
Example: What is the rate of acceleration?
• Two people are pushing a stalled car. The mass of the car is 1850 kg. One person applies a 275 N force while the other applies a 395 N force. A third force of 560 N acts in in the opposite direction compared to the two people. What is the acceleration of the car?
![Page 9: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/9.jpg)
Diagram the problem
Fnet = Fperson 1 + Fperson 2 – Fopposing force
![Page 10: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/10.jpg)
State the Known and Unknowns
• What is known?– Mass (m) = 1850 kg– Force of person #1 (N) = 275 N– Force of person#2 (N) = 395 N– Opposing Force (N) = 560 N
• What is not known?– Acceleration (a) = ?
![Page 11: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/11.jpg)
Perform Calculations
Fnet = Fperson 1 + Fperson 2 - Fopposing Where:Fnet = ma
Substitute for Fnet and solve for a:ma = Fperson 1 + Fperson 2 - Fopposing
a = (Fperson 1 + Fperson 2- Fopposing)/ma = (275 N + 395 N – 560 N)/1850 kga = 0.059 m/s2
If there was no opposing force, how would the rate of acceleration change?
What do you think is the source of the opposing force?
It would increase.
Friction.
![Page 12: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/12.jpg)
Misconceptions about Forces
Is a force required after a ball is released while throwing to make it continue in its path? No: once the contact force between the hand
and the ball are broken, there is no longer a force propelling the ball forward.
![Page 13: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/13.jpg)
Misconceptions about Forces
• Is inertia a force?– No: Inertia is the tendency for an object to
resist a change in velocity.– Inertia is a property of matter.– The more mass an object has, the more
inertia it has.– Forces that exist in the environment act on
objects.
![Page 14: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/14.jpg)
What’s the difference between mass and weight?
• Mass is a property of an object that quantifies (provides a numerical value) for the amount of matter (protons and neutrons) that it contains.
• Weight is a measure of the force of attraction on a body that is directly related to the amount of mass and gravity.
• Mass is the same everywhere, while weight will change with distance from other bodies.
NOTE: MASS AND INERTIA ARE THE SAME!
![Page 15: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/15.jpg)
Determining Weight
• If the mass of an object is known, its weight can be determined using Newton’s 2nd Law of Motion. Fg = mg
Where:• m = mass• g = acceleration due to gravity (g = 9.81 m/s2).
![Page 16: Blue Cow- Recall F net = ma](https://reader036.vdocuments.us/reader036/viewer/2022062722/568139c0550346895da166b8/html5/thumbnails/16.jpg)
Example: Mass vs. Weight
• On Earth:– Mass = 1 kg – Weight = 9.8 N
• On the Moon:– Mass = 1 kg– Weight = 1.62 N (gm = 1.62 m/s2)
• Why is the weight on the moon so much less?– Because the gravitational force of attraction on the
moon is 1/6th that on Earth.