Newton’s Second Law/Force Body Diagrams
By:Brian Kidawa
Chris Hayden
Shoeb Siddiqui
Mike Murphy
Terms
• Force-Agent that results in accelerating or deforming an object.
• Net Force-sum of all forces on an object
• gravity-Attraction between two masses according to their mass.(9.8 m/s)
• Weight-Force of gravity on an object
• Normal Force-Force perpendicular to surface.
• Acceleration-Change of velocity due to a force over time.
• Equilibrium-Net force on an object is zero.
Newton’s Second Law
• Newton’s Second Law states: acceleration of a body is directly proportional to the net force on it and inversely proportional to its mass.
• F=ma
Concepts
• Says that an unbalanced force causes a change on motion.
• Most familiar form of Newton’s Second Law is F=ma.
• If forces are unbalanced, acceleration occurs.
• An object has equilibrium when all forces cancel out.
Reality Check!
• Weapons (guns)
• Cars
• Solar System
• People on chairs
• Sports
Sample Problems
• If the mass of a crate is 100 kg and sliding friction is 250 N, what is the acceleration of the crate when the pulling force is 500 N?
• m=100 kg a=? Pf=500 N Ff=250 N
• Fnet=ma Fnet=500-250 250N
• 250 N=100kg * a a=2.5N/Kg
Sample Problems continued..
• An object of mass 70kg is accelerated by a force of 20 N. What’s is its acceleration?
• F=20 N m=70kg a=?
• 20 N= 70kg*a
• a=.29 N/Kg
Quiz
• A 75 kg person traveling at a constant velocity on ice skates experiences a force of 40 N. What is the person’s acceleration?
• answer:a=0 m/s/s • What is the mass of an object that is
accelerated at 25 m/s/s that is pushed with a force of 500 N.
• answer: m=20 kg
Quiz continued…
• A constant force acts on a 5 kg object and reduces its velocity from 7 m/s to 3 m/s in a time of 3 seconds. Find the amount of force acting on it.
• answer: F=6.65 N• A stock boy pushes a 20 kg box of SPAM with a force of
70 N and it accelerates at 0.4 m/s/s. Find the net force on the SPAM box.
• answer: 8N• A 60m kg man rides up in an elevator that is accelerating
at 0.8 m/s/s. What is the net force on the man?• answer: 48 N
Top Related