# Shared Flashcard Set

## Details

Carly GP2 Physics
Carly GP 2 Physics
40
Physics
11/09/2010

Term
 What is the official statement of newton's 1st Law of Motion?
Definition
 An object at rest remains at rest and an object in motion remains in motion at a constant velocity unless acted upon by an unbalanced object.
Term
 Official statement of Newton's 2nd Law of Motion?
Definition
 A body of mass m subject to a force F undergoes an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force and inversely proportional to the mass, i.e., F = ma. Alternatively, the total force applied on a body is equal to the time derivative of linear momentum of the body.
Term
 What is inertia?
Definition
 The tendency of objcts to resist a change in motion
Term
 How do you determine which object has more inertia?
Definition
 Whichever one has more mass has more inertia.
Term
 Would it be easier to push a car on the moon or Earth?
Definition
 It's the same because of you are opposing its inertia.
Term
 Would it be easier to lift a car on the moon or Earth?
Definition
 The moon, because you are opposing its weight, and also because there is less gravity.
Term
 What is mass?
Definition
 1. The amount of matter in an object.2. The measurement of an object's inertia.
Term
 What is weight?
Definition
 The force of an object due to gravity.
Term
 What are the units of mass and weight?
Definition
 Mass = grams, weight = newtons
Term
 Are mass and weight the same thing?
Definition
 No!
Term
 Are mass and weight in any way proportional?
Definition
 Yes, directly proportional.
Term
 When can the mass of an intact object change?
Definition
 Never!
Term
 Mass and volume are not necessarily proportional. Why?
Definition
 Density
Term
 Newton's second law of motion in equation form. What happens to acceleration if you change mass or the net force by a certain amount? What three forms can this equation be written in?
Definition
 1. Acceleration = net force/mass  2. Acceleration and Force are directly proportional, Acceleration and Mass are inversely proportional  3. Acceleration is in the direction of the net force.
Term
 Finding the net force.
Definition
 Add forces in one direction and subtract smaller from larger.
Term
 Is force a vector or scalar quantity? Why?
Definition
 Vector because it involves both direction and magnitude
Term
 What is the normal force?
Definition
 A force produced by a surface an object is resting on, created by the atoms in the surface (atoms are like tiny springs)
Term
 Direction of acceleration based on the net force
Definition
 A is in the direction of the NF
Term
 What does the magnitude of the friction force depend on?
Definition
 Weight, materials that are made of (NOT SURFACE AREA)
Term
 Study equilibrium table!
Definition
 in notes
Term
 Can an object in motion be in equilibrium? Explain.
Definition
 Yes, if it's at a constant velocity. (dynamic equilibrium)
Term
 How much force must you exert to slide a box over a floor at constant velocity?
Definition
 Friction force is equal and opposite
Term
 Official statement of newton's 3rd law of motion.
Definition
 (see notes) For every action, there is an there is a reaction. This reaction force is equal and opposite to the action force
Term
 What are the two force in Newton's 3rd law called?
Definition
 action, reaction
Term
 Describe the timing of the two forces in Newton's 3rd Law of Motion.
Definition
 simultaneously
Term
 Check your understanding:While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. This is a clear case of Newton's third law of motion. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus?
Definition
 Trick Question! Each force is the same size. For every action, there is an equal ... (equal!). The fact that the firefly splatters only means that with its smaller mass, it is less able to withstand the larger acceleration resulting from the interaction. Besides, fireflies have guts and bug guts have a tendency to be splatterable. Windshields don't have guts. There you have it.
Term
 Check your understanding:Many people are familiar with the fact that a rifle recoils when fired. This recoil is the result of action-reaction force pairs. A gunpowder explosion creates hot gases that expand outward allowing the rifle to push forward on the bullet. Consistent with Newton's third law of motion, the bullet pushes backwards upon the rifle. The acceleration of the recoiling rifle is ... a. greater than the acceleration of the bullet. b. smaller than the acceleration of the bullet. c. the same size as the acceleration of the bullet.
Definition
 The force on the rifle equals the force on the bullet. Yet, acceleration depends on both force and mass. The bullet has a greater acceleration due to the fact that it has a smaller mass. Remember: acceleration and mass are inversely proportional.
Term
 The forces described in Newton's 3rd Law of Motion always act in...
Definition
 pairs
Term
 Example of a skydiver falling to the Earth or a rifle firing a bullet. Compare the force each exerts on the other. Which will accelerate more and why?
Definition
 The force exerted is the same, the one with smaller mass accelerates more (skydiver, buller)
Term
 How must one decide which force is the action force and which force is the reaction force?
Definition
 It doesn't matter which is which
Term
 Does the action force act on the same object as the reaction force?
Definition
 No!
Term
 Is momentum associated with objects in motion, objects at rest, or both?
Definition
 motion
Term
 What is the equation for momentum when direction matters, and when direction doesn't matter?
Definition
 Momentum=mass x velocity  OR Momentum= mass x speed
Term
 Momentum changes when ______ or _______ changes.
Definition
 mass or velocty
Term
 What is required to change momentum?
Definition
 Velocity
Term
 The amount momentum changes is based on the _______
Definition
 impulse
Term
 What is the equation for impulse?
Definition
 Impulse = force x time
Term
 Brick wall vs. Haystack situation. Be able to explain this situation in depth!
Definition
 The change in momentum is the same in both cases, therefore, the impulse is the same in both cases. For haystack, time of impact is greater so the force is less. For brick, time of impact is less so the force of impact is rgeater.
Term
 Provide two reasons why it is clear momentum and inertia are not the same thing.
Definition
 1. Momentum depends on mass and velocity, while inertia depends on just mass. 2. Momentum is only for onjects in motion and inertia is for objects in motion and at rest.
Term
 What type of force is required to change momentum?
Definition
 unbalanced, external force
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