問題一覧
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is one that has nothing to do with a special direction. many physical concept such as length time temperature mass density charge and volume are scalars; each has a scale or size but no associated direction.
scalar quantity
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is one that has be specified completely only if we provide both its magnitude (size) and direction. many physical concepts such as displacement velocity acceleration force and momentum are vector quantities.
vector quantity
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or sun of a number of vectors of a particular type is that single vector that would have the same effect as all the original vectors taken together
resultant
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this method for finding the resultant of a several vectors consists in beginning at any convenient point and drawing each vector arrow in turn in they may be taken in any order of succession the tail end of each arrow is position at the tip end of the proceeding one
graphical addition of vectors
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are defined in the relation to a right angle.
trigonometric function
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it is effective value in a given direction. for example the x component of a displacement is the displacement parallel to the x-axis caused by the given displacement.
component of a vector
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each vector is dissolved into x -, y -, nc components, with negatively directed components taken as negative
component method
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have a magnitude of 1 and are represented by the bold face symbol top with a caret
unit vectors
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when an object moves from one point in space to another the displacement is the vector from the initial location to the final location. it is independent of the actual distance travel
displacement
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is a scalar quantity. if an object takes a time interval t to travel a distance l, then average speed equals total distance travel over time taken
speed
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is a vector quantity. if an object undergoes a vector displacement s in a time interval t then average velocity equals vector displacement over time taken
velocity
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measures the time rate of a change of velocity average acceleration=change in velocity vectors/time taken
acceleration
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is a constant and lies along the line of displacement vector
acceleration vector
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either the direction may be chosen as positive. if a displacement velocity or acceleration is in the opposite direction. it must be taken as _____________.
negative
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is the average velocity evaluated for a time interval that approaches zero
instantaneous velocity
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it is an object at a certain time is the slope of a velocity versus time graph at that time
instantaneous acceleration
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the acceleration of a body moving only under the force of gravity, which is directed vertically downward
gravitational
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the _________ of an object is measure of the inertia of the object
mass
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is the tendency of a body at rest to remain at rest, end of a body in motion to continue moving with unchanged velocity
inertia
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is an object whose mass is defined to be 1 kg. the masses of other object are found by comparison with this mass. a gram mass is equivalent to exactly 0.001 kg
standard kilogram
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is the agency of change. in mechanics it is that which changes the velocity of an object. it is a vector quantity having magnitude and direction
force
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is one whose source lies outside of the system being considered
external force
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acting on an object causes the object to accelerate in the direction of that force
net external force
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an object at rest will remain at rest; an object in motion will continue in motion with constant velocity, except in so far as it's acted upon by an external force.
newton's first law
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as stated by newton, it was framed in terms of the concept of momentum.
newton's second law
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it is a newton's law that matter interact with matter--forces come in pairs. this is often called the law of action and reaction
newton's third law
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when two masses m and m' gravitationally interact, they interact each other with forces of equal magnitude. for point masses or spherically symmetric bodies, the attractive force Fg is given by FG=G mm'/r²
law of universal gravitation
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is the gravitational force acting downward on the object. on the earth it is gravitational force exerted on the object by the planet. its unit are newtons in the SI and pounds in the british system
weight
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falling freely toward the earth's in subject to only one force
mass
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acting on a string or chain or tendon is the applied force tending to stretch it.
tensile force
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the magnitude of the tensile force
tension
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is a tangential force acting on an object that opposes the sliding of the object on adjacent surface with which it in contact. it is parallel to the surface and opposite to the direction of the motion or of impending motion
friction force
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on an object that is being supported by the surface is the component of the supporting force that is perpendicular to the surface
normal force
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is defined for the case in which one surface is sliding across another at constant speed
coefficient of kinetic friction
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is defined for the case in which one surface is just on the verge of sliding across another surface
coefficient of static friction
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are forces whose lines of action all pass through a common point. the forces acting on it point object because they all pass through the same point, the point object.
concurrent forces
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under the action of concurrent forces provide it is not accelerating
equilibrium
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is essentially the force with which gravity pulls downward upon it
weight
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about an axis, due to a force, is a measure of the effectiveness of the force in producing rotation about that axis.
torque
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what is the units of torque
newtons-meters
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a torque that tends to cause counterclockwise rotation about the axis is
positive
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the torque the tense to cause clockwise rotation about the axis is
negative
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is the point at which the entire weight of the object may be considered concentrated
center of gravity
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done by a force is defined as the product of that force times the parallel distance over which it acts.
work
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the si unit of work
newton-meter
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is a measure of the change imparted to a system. it is given to an object when a force does work on the object
energy
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is the energy possessed by an object because it is in motion. if an object of mass m is moving with a speed v, it has translational KE
kinetic energy
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is the energy possessed by an object because of the gravitational interaction
gravitational potential energy
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it can neither be created nor destroyed, but only transform from one kind to another
energy
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is the time rate of doing work or the rate of transfer of energy
power
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what is the si unit of power
watt
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is the product of its mass and velocity
linear momentum
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is a vector quantity whose direction is that of the velocity. the unit are kg•m/s
momentum
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is the product of a force and the time interval over which the force acts
impulse
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is one in which the sum of the translational KEs of the object is not changed during the collision
perfectly elastic collision
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for any collision between two bodies in which the body's move only along a single straight line
coefficient of restitution
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is usually expressed in radians, in degrees, or in revolutions
angular displacement
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whose axis of rotation is fixed is the rate at which its angular coordinate, the angular displacement, changes with time
angular speed
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whose axis of rotation is fixed in the rate at which its angular speed changes with time
angular acceleration
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a point mass m moving with constant speed v around a circle of radius is undergoing acceleration. although the magnitude of its linear velocity is not changing, the direction of the velocity is continually changing
centripetal acceleration
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is the force that must act on a mass moving in circular path of radius to give it the centripetal acceleration
centripetal force
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is a measure of the rotational inertia of the body. if an object that is free to rotate about an axis is difficult to set into rotation
moment of inertia
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acting on a body of moment of inertia, produces in it an angular acceleration
torque and angular acceleration
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done on a rotating body during an angular displacement by a constant torque is even by W= torque(teta)
work
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transmitted to a body by a torque is given by P=(torque)(angular speed)
power
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is a vector quantity that has magnitude and is directed along the axis of rotation
angular momentum
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has a magnitude torque times time worthy is the time during which the constant torque acts on the object
angular impulse
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the moment of inertia of a body about an axis parallel to an axis through the center of a mass
parallel-axis theorem
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p of a material it is mass per unit volume
mass density
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the si unit of mass density
kg/m³
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is the ratio of the density of the substance to the density of some standard substance. It is usually water (4°C) for liquids and solids while for gases, it is usually air
specific gravity
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is the property by which of body returns to its original size and shape when the forces that deform it are removed
elasticity
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experience within a solid is the magnitude of the force acting, divided by the area over which it acts
stress
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what is the si unit for stress
pascal
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is the fractional deformation resulting from a stress. it is measured as the ratio of the change in some dimension of the body to the original dimension in which the change occurred
strain
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is the smallest stress that will produce a permanent distortion in the body. when a stress in excess of this limit is applied, the body will not return exactly to its original state after the stress is removed
elastic limit
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is the modulus of elasticity
young's modulus
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describe the volume elasticity of a material. suppose that i uniformly distributed comprehensive force acts on the surface of an object and is directed perpendicular to the surface at all points
bulk modulus
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what is the si unit of pressure
Pascal
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describe the shape elasticity of a material.
shear modulus
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what is the standard atmospheric pressure
1.01×10⁵ Pa
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due to a column of fluid of height and mass density
hydrostatic pressure
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when the pressure on any part of a confined fluid liquid or gas is changed, the pressure and every other part of the fluid is also changed by the same amount
pascal's principle
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a body woolly or partly immerse in a fluid is buoyed up by a force equal to the weight of the fluid it deplays. it can be considered to act vertically upward through the center of the gravity of the displace fluid
archimedes' principle
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when a fluid that fills in a pipe flows through the pipe with an average speed
flow or discharge
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is the rate at which the shares train within the fluid is changing
shear rate
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it is a fluid that measure of how large a shear stress is required to produce unit shear rate
viscosity
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the fluid flow through a cylindrical pipe of length and cross sectional radius is given by
poiseuille's law
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for the study flow of a continuous stream of fluid: considered two different points along the stream path
bernoulli's equation
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suppose that attack contains liquid and is open to the atmosphere at its top
torricelli's theorem
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is a dimensionless number that applies to a fluid of viscosity and density flowing with speed through a pipe with diameter
reynolds number
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maybe measured on the celsius scale, on which the freezing point of water is 0° c, and the boiling point is at 100° c
temperature
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scale is displaced 273.15 celsius
kelvin
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is the random kinetic energy of the particles (usually electrons ions atoms and molecules) composing a system
thermal energy
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is a thermal energy in transit from a system at one temperature to a system that is in contact with it, but is at lower temperature
heat
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is the quantity of heat required to change the temperature of unit mass of the substance by 1°
specific heat