CH8: Newton's Laws of Motion Flashcards
Is force a spatial quantity?
Yes
What did Aristotle [384 BC – 322 BC] do?
Aristotle used force to explain how motion could be created. Force is the impetus to motion.
What did Galileo [1564 – 1642] do?
- Force causes change in velocity
- Gravity pulls an object towards the ground
- Effect of gravity is independent of an object’s mass
What did Newton [1643 – 1727] do?
Developed mathematical formulations for force, including gravity
What is a Force?
A push or pull exerted on one object by another object
A force can attract or __________
repulse
Do objects have to be in direct contact to exert a force?
No. – “Action at a distance” – gravity, electromagnetism
Does exerting a force always cause a change in motion?
No. Exerting a force may or may not cause a change in motion. However, forces are acting all around us, with no motion present. Sometimes, forces are exerted to prevent motion from occurring.
What are the four fundamental forces of the universe?
- Strong
- Electromagnetic
- Weak Interaction
- Gravity
Strong force description:
Attraction
Relative Strength: 1
Range (m): 10^-15
Electromagnetic force description:
Attraction or Repulsion
Relative Strength: 1/137
Range (m): Infinite
Weak Interaction force description:
Attraction or Repulsion
Relative Strength: 10^-6
Range (m): 10^-18
Gravity force description:
Attraction
Relative Strength: 6 x 10^-139
Range (m): Infinite
What is the Earth’s mass?
5.9723 x 1024 kg
What is the Earth’s radius?
~6371 km
Two objects, both having mass, with a distance between the center of the objects (r). How does gravitational force come into play?
Object 1 will exert a force on object 2, and object 2 will exert a force on object 1. The amount of force exerted by object 1 on object 2 is equal in magnitude to the force exerted by object 2 on object 1. This is the gravitational force (Fg) that acts between these two objects.
How to calculate gravitational force?
Fg = G(m1m2)/r^2
Relationship between gravitational force and mass
Gravitational Acceleration is Mass Independent
What are the two events in weightlifting?
- The snatch
- Clean and jerk
What is the snatch?
Where a barbell is lifted from the ground to
above the head
What is the clean?
Where a barbell is lifted from the ground to
above the shoulders
What is Newton’s first law of motion?
Inertia & Equilibrium: The first law states that an object’s velocity is constant unless an unbalanced force is applied to the object.
What is Newton’s second law of motion?
Dynamics: The second law states that when an unbalanced force is applied to an object, the velocity of the object will change. In other words, the object will accelerate.
What is Newton’s third law of motion?
Force pairs: The third law states that forces act in pairs, where object A will exert a force on object B, and a force of equal magnitude and opposite direction will be exerted on object A by object B.
What is equilibrium?
There is no change in velocity, therefore acceleration is 0. Since there is no net force acting on the object, there is no impulse applied and momentum does not change. In equilibrium, there may be forces acting on an object. However, the vector sum of these forces is equal to zero.
What is static equilibrium?
A special condition of equilibrium occurs when velocity itself is zero
What is inertia?
The resistance to a change in equilibrium. Inertia can take the form of mass, or moment of inertia. Equilibrium is maintained as objects have inertia.
What is dynamics?
In dynamics, change in velocity is not zero, therefore there is acceleration present. Since there is a net force applied to the object, impulse is applied, therefore, there will be a change in momentum. The forces acting on the object are unbalanced
Unbalanced force creates an __________, proportionate to the mass of the object
acceleration, F = ma
What is the Impuse-Momentum Relation?
The effect of a force. The application of an impulse results in a change in momentum. Impulse is applied when force is applied over a period time. Change in momentum is the change in velocity of a mass. We assume that mass is constant.
What is impulse?
Certain amount of force you apply for a certain amount of time to cause a change in momentum
What is momentum?
Measure of the amount of motion in an object
What is reaction forces?
Exerting a force will result in a reaction force.That is object A can exert a force on object B, if and only if, object B exerts a force on object A.
What is “action-reaction”?
The force of B on A must be equal in magnitude, opposite in direction, and collinear to the force of A on B.
