Download - Forces and newton’s laws
![Page 1: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/1.jpg)
Forces and Newton’s Laws
Ch 6, 7.1
![Page 2: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/2.jpg)
Force
• a push or a pull
• Measured in Newtons (N)
![Page 3: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/3.jpg)
Types of Forces
![Page 4: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/4.jpg)
Gravitational Force
• Attractive force that exists between all objects• Weakest of the 4 forces, but acts over the
longest distance
![Page 5: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/5.jpg)
Electromagnetic
• Gives materials their strength, ability to bend, squeeze, stretch, etc.
![Page 6: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/6.jpg)
Strong Nuclear Force
• Holds the particles in a nucleus together• strongest of the 4 forces, but acts over the
smallest distance.
![Page 7: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/7.jpg)
Weak force
• Involved in the radioactive decay of some nuclei• form of the electromagnetic force
![Page 8: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/8.jpg)
Newton’s Laws of Motion
![Page 9: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/9.jpg)
1st Law - Inertia
• Any object will continue at constant velocity until acted on by some outside force.
![Page 10: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/10.jpg)
2nd Law - F=ma
• The acceleration of an object is directly proportional to the net force on it and inversely proportional to its mass.
![Page 11: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/11.jpg)
3rd Law - Action-Reaction pairs
• For every action there is an equal and opposite reaction.
![Page 12: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/12.jpg)
Question
• The horse knows if he pulls with 100N of force and the carriage pulls back with 100 N of force then the carriage isn’t going to move. Is his logic right?
![Page 13: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/13.jpg)
Net Force vs Action-Reaction Pairs
• Action-reaction pairs work on different objects and they are always equal to opposite; EX: I pull on the cart and the cart pulls on me.
• Net force is the sum of all forces and it causes acceleration; the forces work on the same object; EX: I pull on the cart and friction pulls on the cart.
![Page 14: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/14.jpg)
Mass vs Weight
• Mass - amount of matter or inertia an object has.
• Weight - gravitational force exerted by the earth on an objects mass.
• W=mg
• Normal Force - force that is perpendicular to the contact surface.
![Page 15: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/15.jpg)
Friction
• Force that opposes motion between 2 surfaces that are in contact.
![Page 16: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/16.jpg)
Types of Friction
![Page 17: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/17.jpg)
Static Friction
• Force that opposes the start of motion.
![Page 18: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/18.jpg)
Sliding (Kinetic) Friction
• Force that opposes motion once the object is moving.
• Note: Static friction is greater than sliding friction because of Newton’s First Law
• Ff = μN
![Page 19: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/19.jpg)
Example Problems
• A 12 kg box that is pulled across the floor at 2 m/s2 with a force of 40 Newtons. Find the coefficient of friction.
• A 400 kg crate is accelerated upward at 3 m/s2 by a crane. Find the tension in the cable.
![Page 20: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/20.jpg)
Equilibrant
• Force equal and opposite to the resultant.
• Ex: Find the equilibrant for 20 N @ 125 degrees.
• Answer: 20 N @ 305 degrees
![Page 21: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/21.jpg)
Example Problems
• A 30 kg box is on a 35 degree incline plane. Find:
• A. The force that causes the box to move down the incline.
• B. The normal force.
• C. The acceleration if μ = 0.25
![Page 22: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/22.jpg)
• A 400 kg sign is hung by cables that are 110 degrees apart. Find the tension in each cable.
![Page 23: Forces and newton’s laws](https://reader035.vdocuments.us/reader035/viewer/2022081419/557e2106d8b42abc648b5568/html5/thumbnails/23.jpg)
• A 50 kg box is pulled across the ground with a force of 300 Newtons @ 35 degrees and μ = 0.3. Find the acceleration.