Unit 3- Dynamics and Circular Motion Flashcards
What is a force?
A push or a pull that is measured in Newtons (N).
Explain Contact vs. Non Contact Forces
Contact Forces- Where one object exerts a force on another object when they touch each other. (Force of Friction, Applied Force, Tension, Normal Force)
Non-Contact Forces- Where two objects don’t need contact to exert a force on each other. (Force of gravity)
Explain the Following Forces:
1. Force of Friction
2. Applied Force
3. Tension
4. Normal Force
5. Force of Gravity
- Exists between objects in motion (kinetic friction) or objects attempting to be in motion (static friction). This force always opposes motion.
- A push or a pull from a human action, machine, etc.
- When the applied force is exerted on a rope or a string (goes in both directions at once)
- A support force that acts perpendicular to a surface.
- Attractive force between all objects (but we only do the math for large masses)
What is Newton’s first law of motion?
An object in motion stays in motion. An object at rest stays at rest. Unless acted upon by a net force. This means that:
- A net force is notrequired for an object to maintain a constant velocity.
- If a net force exists, acceleration occurs.
Note: This law is also sometimes called the law of inertia, where inertia is the ability to resist change.
Do all objects have inertia?
Yes, all objects have inertia, but objects with larger masses have more. Mass (kg) is measure of the amount of matter in an object. DO NOT CONFUSE MASS WITH WEIGHT! Weight is the force of gravitational attraction. Mass is constant throughout the universe but weight changes depending on location.
What is Newton’s second law of motion?
If a new force exists, the object will accelerate in the direction of the net force. The magnitude of the acceleration is direction proportional to the net force and inversely proportional to the mass of the object.
What is friction?
Friction is created when two surfaces move, or attempt to move past one another. On the microscopic level, irregularities in the surfaces ‘catch’ on each other. Because of this, the nature of both surfaces combine to create a coefficient of kinetic friction.
What is the difference between static and kinetic friction?
Static Friction- Friction on an object that is at rest.
Kinetic Friction- Friction on a moving object.
What is uniform circular motion?
Motion in a circular path at a constant speed.
Explain how velocity, acceleration, and the term centripetal are related to the circle?
- The velocity at any time is tangent to the circle.
- The acceleration of the object is always towards the center
- These two terms are the definition of centripetal which means center seeking.
Why is anything travelling in a circular path accelerating?
Even though it may be traveling at a constant speed, anything travelling in a circular path is accelerating because the direction of its velocity is always changing.
What is centripetal force?
When acceleration occurs in a circular direction. It is the net force that accelerates an object towards the center of its circular path.
In what direction will moving objects tend to move?
Moving objects tend to travel in straight lines unless acted upon by an unbalanced force. An unbalanced force, the centripetal force, is required for objects moving in circles. The centripetal force is not a separate force, centripetal is simply an adjective. This net force can be supplied by any force or combination of forces, but it must be directed towards the center of the circle.
What force causes the centripetal force in the following situations:
1) A mass is twirled in a circle at the end of a string
2) When a car rounds a corner on a highway
3) When the moon orbits the Earth
1) tension, T
2) Friction, Ff
3) gravity, Fg
If a mass is spun with just enough speed to swing it in a circular path, what is the tension in the string at the top?
0
We say that the mass at the peak of its arc is weightless, because the net force working on it is only gravity. This is the same as an object in a total free fall. Thus for this special case we use a special equation.
What is the centrifugal force?
The centrifugal force does not actually exist. It is simply the apparent force that causes a rotating object to move in a straight line. In reality what we seem to feel as the centrifugal force is inertia.
Which of the following are true?
A. A force is a push or a pull exerted upon an object.
B. Forces always cause objects to move.
C. An object can experience two or more forces and not accelerate.
D. A force is a vector quantity; there is always a direction associated with it.
ACD
Which of the following are true?
A. It would take an unbalanced force to keep an object in motion.
B. If an object is at rest, then there are no forces acting upon the object.
C. It would take an unbalanced force to keep an object in motion at a constant velocity.
D. It is the natural tendency of all objects to eventually come to a rest position.
E. It would take an unbalanced force to cause an object to accelerate.
F. An object which is moving rightward has a rightward force acting upon it.
E
Which of the following statements are true?
A. If an object is accelerating to the right, the net force on the object must be directed towards the right.
B. If an object is moving to the right and slowing down, then the net force on the object is directed towards the left.
C. Accelerating objects are either speeding up or slowing down.
D. The acceleration of an object is directly dependent upon is mass and inversely dependent upon its net force.
AB
