Kinematics and Dynamics Flashcards
instantaneous vs average velocity vs average speed
instantaneous is the change in position for a time
Average velocity (vector) is the ratio of displacement vector over change in time
average speed (scalar) is the ratio of distance traveled/ change in time
distance vs displacement
Distance is the length of the path taken by an object whereas displacement is the simply the distance between where the object started and where it ended up.
magnitude of gravitational force between 2 objects
what is friction?
Friction is a type of force that opposes the movement of objects. Unlike other kinds of forces, such as gravity or electromagnetic force, which can cause objects either to speed up or slow down, friction forces always oppose an object’s motion and cause it to slow down or become stationary. There are two types of friction: static and kinetic.
what is static friction?
Static friction (fs) exists between a stationary object and the surface upon which it rests
if object on resting surface with no ex force the static friction is 0
Friction is a type of force that opposes the movement of objects. Unlike other kinds of forces, such as gravity or electromagnetic force, which can cause objects either to speed up or slow down, friction forces always oppose an object’s motion and cause it to slow down or become stationary. There are two types of friction: static and kinetic.
explain
This setup implies that the maximal value of static friction is somewhere between 50 and 100 N; any applied force less than this threshold will not be sufficient to move the bag as there will be an equal but opposite force of static friction opposing the bag’s motion.
how does contact area relate to force?
contact point are were friction occurs
increase in contact areas increases friction
what is kinetic energy?
does KE always occur when a wheel is rolling on a road —?
Kinetic friction (fk) exists between a sliding object and the surface over which the object slides.
A wheel, for example, that is rolling along a road does not experience kinetic friction because the tire is not actually sliding against the pavement. The tire maintains an instantaneous point of static contact with the road and, therefore, experiences static friction. Only when the tire begins to slide on, say, an icy patch will kinetic friction come into play. Any time two surfaces slide against each other, kinetic friction will be present and its magnitude can be measured according to this equation:
does the contact area or surface area or velocity effect KE friction?
This means that kinetic friction will have a constant value for any given combination of a coefficient of kinetic friction and normal force. It does not matter how much surface area is in contact or even the velocity of the sliding object
which is always larger static or kinetic friction coefficient?
The value of μs is always larger than the value of μk. Therefore, the maximum value for static friction will always be greater than the constant value for kinetic friction: objects will “stick” until they start moving, and then will slide more easily over one another
It always requires more force to get an object to start sliding than it takes to keep an object sliding.
mass versus weight
Mass (m) is a measure of a body’s inertia—the amount of matter in the object. Mass is a scalar quantity, and, as such, has magnitude only. The SI unit for mass is the kilogram, which is independent of gravity. One kilogram of material on Earth will have the same mass as one kilogram of material on the Moon.
Weight (Fg), on the other hand, is a measure of gravitational force (usually that of the Earth) on an object’s mass. Because weight is a force, it is a vector quantity with units in newtons (N).
how are mass and weight related?
how to find center of mass?
if we model a tennis racket with the one point that always moves in simple parabolic motion
What is center of gravity?
The center of gravity is related and corresponds to the single point at which one can conceptualize gravity acting on an object. Only for a homogeneous body (with symmetrical shape and uniform density) should one expect the center of gravity to be located at its geometric center.
The center of mass of a uniform object is at the __________ of the object.
The center of mass of a uniform object is at the geometric center of the object.
what is acceleration?
Acceleration (a) is the rate of change of velocity that an object experiences as a result of some applied force. Acceleration, like velocity, is a vector quantity and is measured in SI units of meters per second squared.
what is deacceleration vs negative acceleration
Deceleration always refers to acceleration in the direction opposite to the direction of the velocity. Deceleration always reduces speed. Negative acceleration, however, is acceleration in the negative direction in the chosen coordinate system.
what is average acceleration?
what is instantaneous acceleration?
newtons first law
A body either at rest or in motion with constant velocity will remain that way unless a net force acts upon it. This is also known as the law of inertia. Newton’s first law ought to be thought of as a special case of his second law, which is described next.
newtons second law
What Newton’s second law states is actually a corollary of the first: An object of mass m will accelerate when the vector sum of the forces results in some nonzero resultant force vector. No acceleration will occur when the vector sum of the forces results in a cancellation of those forces. Note that the net force and acceleration vectors necessarily point in the same direction.
newtons third law
To every action, there is always an opposed but equal reaction. More formally, the law states that for every force exerted by object A on object B, there is an equal but opposite force exerted by object B on object A. For example, when you hit your hand against your desk, your hand exerts a force on the desk. Simultaneously, the desk exerts a force of equal magnitude in the opposite direction on your hand. Physical contact is not necessary for Newton’s third law; the mutual gravitational pull between the Earth and the Moon traverses hundreds of thousands of kilometers of space.
what is linear motion?
In linear motion, the object’s velocity and acceleration are along the line of motion, so the pathway of the moving object continues along a straight line.
what are vector components for inclined plane?
what is uniform circular motion?
In uniform circular motion, the instantaneous velocity vector is always tangent to the circular path, as shown in Figure 1.9. What this means is that the object moving in the circular path has a tendency (inertia) to break out of its circular pathway and move in a linear direction along the tangent. It is kept from doing so by a centripetal force, which always points radially inward. In all circular motion, we can resolve the forces into radial and tangential components. In uniform circular motion, the tangential force is zero because there is no change in the speed of the object.
centripetal force and centripetal acc
As a force, the centripetal force generates centripetal acceleration. Remember from the discussion of Newton’s laws that both force and acceleration are vectors and the acceleration is always in the same direction as the net force. Thus, it is this acceleration generated by the centripetal force that keeps an object in its circular pathway. When the centripetal force is no longer acting on the object, it will simply exit the circular pathway and assume a path tangential to the circle at that point. The equation that describes circular motion is
what is rotational motion?
Rotational motion occurs when forces are applied against an object in such a way as to cause the object to rotate around a fixed pivot point, also known as the fulcrum.
Application of force at some distance from the fulcrum generates torque (τ) or the moment of force. The distance between the applied force and the fulcrum is termed the lever arm. It is the torque that generates rotational motion, not the mere application of the force itself. This is because torque depends not only on the magnitude of the force but also on the length of the lever arm and the angle at which the force is applied. The equation for torque is a cross product:
