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# MCAT Physics

Question | Answer |
---|---|

a branch of mechanics which provides the basic tools for describing the motion of objects | kinematics |

the rate of change of the velocity | acceleration |

the rate of change of the position | velocity |

a continuous change in the position of a body relative to a reference point | motion |

magnitude of the velocity | speed |

numerical description of how far apart objects are at any given moment in time | distance |

the vector that specifies the position of a point or a particle in reference to an origin or to a previous position | displacement |

a simple physical quantity that does not depend on direction, and is therefore not changed by coordinate system rotations | scalar |

a physical quantity characterized by both magnitude and direction | vector |

motion in which an object moves with constant speed along a circular path | uniform circular motion |

motion with no acceleration other than that provided by gravity | free fall |

a particular perspective from which the universe is observed, providing a set of axes from which an observer can measure the position and motion of all points in a system | frame of reference |

the path a moving object follows through space | trajectory |

represents the location of an object in space in relation to an arbitrary inertial frame of reference | position vector |

the world's most widely used system of units | international system of units |

the nominal acceleration due to gravity at the Earth's surface at sea level | standard gravity |

the science of mechanics that deals with the motion, behavior, and effects of projectiles | ballistics |

rate of change of the acceleration | jerk |

the fourth derivative of the displacement vector with respect to time, with the first, second, and third derivatives being velocity, acceleration, and jerk, respectively | snap |

anything that can cause a massive body to accelerate. may be experienced as a lift, a push, or a pull | force |

a fundamental concept in physics, roughly corresponding to the intuitive idea of how much matter there is in an object | mass |

the branch of classical mechanics that is concerned with the effects of forces on the motion of objects | dynamics |

a measurement of the gravitational force acting on an object | weight |

the external force required to make a body follow a circular path at constant speed. the force is directed inward, toward the center of the circle | centripetal force |

the force that opposes the relative motion or tendency toward such motion of two surfaces in contact | friction |

a dimensionless quantity used to calculate the force of friction (static or kinetic) | coefficient of friction |

the component, perpendicular to the surface of contact, of the contact force exerted by the surface | normal force |

a force between two objects that are touching each other | contact force |

the SI derived unit of force | Newton |

the property of an object to remain at constant velocity unless acted upon by an outside force | inertia |

a vector produced when two or more forces act upon a single object. also called a resultant | net force |

states that forces occur in pairs, one called the action and the other the reaction | Newton's third law |

a mechanism by which particles interact with each other and which cannot be explained in terms of another interaction | fundamental interaction |

when two solid surfaces slide against each other | sliding friction |

Newton's first and second laws of motion are valid, ie. neither is rotating nor accelerated | inertial frame of reference |

a reaction force applied by a stretched string, rope, or a similar object, upon the objects which stretch it | tension |

the frictional resistance that occurs when an object rolls. it is usually much smaller than sliding friction | rolling resistance |

a unit of force specified in the centimeter-gram-second (cgs) system of units | dyne |

an apparent force that acts on all masses in a non-inertial frame of reference arising from the acceleration of the non-inertial frame itself | fictitious force |

defined as a work one system does (or can do) on another system | energy |

the extra energy which it possesses due to its motion, defined as the work needed to accelerate the body from rest to its current speed | kinetic energy |

energy stored within a physical system | potential energy |

the amount of energy transferred by a force | mechanical work |

states that the total amount of energy in an isolated system remains constant, although it may change forms | conservation of energy |

the rate at which work is performed or energy is transmitted. It is the amount of energy required or expended for a given unit of time | power |

the SI unit of energy | joule |

the SI derived unit of power, equal to one joule per second | watt |

any device that only requires the application of a single force to work | simple machine |

a flat surface whose endpoints are at different heights | inclined plane |

a rigid object that is used with an appropriate fulcrum or pivot point to multiply the mechanical force that can be applied to another object | lever |

a wheel with a groove along its edge for holding a rope or cable or belt | pulley |

the factor by which a mechanism multiplies the force put into it | mechanical advantage |

a unit of energy often used also in theoretical physics as a unit of mass. It is the amount of kinetic energy gained by a single unbound electron when it passes through an electrostatic potential difference of one volt, in vacuo | electronvolt |

a force that does zero net work on a particle that travels along any closed path in an isolated system | conservative force |

the energy which causes or is released by the physical distortion of a solid or a fluid | elastic energy |

the amount of energy required to pull all of the material apart, to infinity, of an object consisting of loose material, held together by gravity alone | gravitational binding energy |

a unit of measurement for energy equal to the amount of heat required to raise a gram of water one degree celsius. In most fields, it has been replaced by the joule | calorie |

an English unit of work or energy. It is the amount of energy expended when a force of one pound acts through a distance of 1 foot along the direction of the force | foot-pound |

a unit of energy used globally in the power, steam generation and heating and air conditioning industries | British thermal unit |

the effectiveness of a machine and is defined as the ratio of mechanical advantage to velocity | mechanical efficiency |

the unit of energy and mechanical work in the centimetre-gram-second (CGS) system of units | erg |

the product in classical mechanics of the mass and velocity of an object | momentum |

a specific point at which, for many purposes, the system's mass behaves as if it were concentrated | center of mass |

the action of bodies striking or coming together | collision |

a collision in which the total kinetic energy of the colliding bodies after collision is equal to their total kinetic energy before collision | elastic collision |

a collision in which some of the kinetic energy of the colliding bodies is converted into internal energy in at least one body such that kinetic energy is not conserved | inelastic collision |

the simple product of the force and time, when both the force and mass are constant | impulse |

states that a particular measurable property of an isolated physical system does not change as the system evolves | conservation law |

equal to the rate of change of the backward momentum resulting when a gun is fired | recoil |

a fractional value representing the ratio of velocities before and after an impact | coefficient of restitution |

a way to describe the efficiency of rocket and jet engines. It represents the impulse per unit of propellant | specific impulse |

a device that demonstrates conservation of momentum and energy. It is constructed from a series of pendulums (usually 5) abutting one another | Newton's cradle |

can informally be thought of as rotational force or angular force which causes a change in rotational motion. It is defined by linear force multiplied by a radius | torque |

a movement of an object in a circular motion, around a center for a point, around a line called an axis for a three dimensional object | rotation |

the measure of the extent to which the object will continue to rotate about that point unless acted upon by an external torque | angular momentum |

specifies the angular speed at which an object is rotating along with the direction in which it is rotating | angular velocity |

the rotational analog of mass. That is, it is the inertia of a rigid rotating body with respect to its rotation | moment of inertia |

the angle through which a point or line has been rotated in a specified sense about a specified axis | angular displacement |

the kinetic energy due to the rotation of an object; sometimes called angular kinetic energy | rotational energy |

a scalar measure of rotation rate. It is the magnitude of the angular velocity | angular frequency |

the rate of change of angular velocity | angular acceleration |

when the sum of the forces and torques on each particle of the system is zero | mechanical equilibrium |

a unit of frequency: the number of full rotations completed in one minute around a fixed axis | revolutions per minute |

the branch of physics concerned with the analysis of loads, ie. forces and torques, on physical systems in static equilibrium | statics |

an idealization of a solid body of finite size in which deformation is neglected | rigid body |

a device based on the principle of conservation of angular momentum. The essence of the device is a spinning wheel on an axle | gyroscope |

the angle subtended by an arc length equal to the radius of the circle | radian |

the SI unit of angular velocity | radian per second |

a system of forces with a resultant moment but no resultant force. Its effect is to create rotation without translation | couple |

a change in the direction of the axis of a rotating object | precession |

a quantity that transforms like a vector under a proper rotation, but gains an additional sign flip under an improper rotation; axial vector | pseudovector |

a rotating disk used as a storage device for kinetic energy | flywheel |

a mechanical model that is used to explain rotating systems. Three angles are required to orient such an object in space | rigid rotor |

the motion of a simple oscillator | simple harmonic motion |

an object that is attached to a pivot point so it can swing freely | pendulum |

a nonnegative scalar measure of a wave's magnitude of oscillation, the magnitude of the maximum disturbance in the medium during one wave cycle | amplitude |

the measurement of the number of occurrences of a repeated event per unit of time | frequency |

a flexible elastic object used to store mechanical energy usually made out of hardened steel | spring |

the weight on the end of a pendulum | bob |

the variation of some measure about a central value (often a point of equilibrium) or between two or more different states | oscillation |

a system which, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement | harmonic oscillator |

the SI unit of frequency; its base unit is the cycle per second | Hertz |

any effect that tends to reduce the amplitude of oscillations of an oscillatory system | damping |

a function that repeats its values after some definite period has been added to its independent variable | periodic function |

the quality of occurring at regular intervals or periods in time or space | periodicity |

the fraction of a cycle corresponding to an offset in the displacement from a specified reference point at time t = 0 | phase |

refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road | vibration |

the tendency of a system to oscillate at maximum amplitude at a certain frequency | resonance |

a useful simplification of the laws of trigonometry which is only approximately true for finite angles, but correct in the limit as the angle approaches zero | small-angle approximation |

having an equal time difference or occurring simultaneously | isochronous |

a system of two simple pendulums on a common mounting which move in anti-phase | double pendulum |

a natural phenomenon by which all objects with mass attract each other | gravitation |

the cyclic rising and falling of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans | tides |

a vector field pointing directly towards the particle giving the magnitude of the force per unit mass for the array of points in space | gravitational field |

the path that an object makes around another object while under the influence of a centripetal force such as gravity | orbit |

the speed where the kinetic energy of an object is equal in magnitude to its potential energy in a gravitational field | escape velocity |

performed in 1797 - 1798, was the first experiment to measure the force of gravity between laboratory masses | Cavendish experiment |

the time it takes a planet (or another object) to make one full orbit | orbital period |

a satellite whose orbital track on the Earth repeats regularly over points on the Earth over time | geosynchronous satellite |

an orbit around the Earth with an orbital period matching the Earth's sidereal rotation period | geosynchronous orbit |

a geosynchronous orbit directly above the Earth's equator, with orbital eccentricity of zero. From the ground, such an object appears motionless in the sky | geostationary orbit |

an elliptic orbit with the eccentricity equal to zero | circular orbit |

the locus of points on a plane where the sum of the distances from any point on the curve to two fixed points is constant | ellipse |

a unit of length nearly equal to the semi-major axis of Earth's orbit around the Sun | astronomical unit |

the point at which an object in orbit around the Earth makes its closest approach to the Earth | perigee |

a term used in astronomy to describe alterations to an object's orbit caused by gravitational interactions with other bodies | perturbation |

the point of greatest or least distance of the elliptical orbit of an astronomical object from its center of attraction | apsis |

the theory that the sun is at the center of the Universe and/or the Solar System | helocentrism |

generally defined as an orbit within the locus extending from the Earth's surface up to an altitude of 2,000 km | low Earth orbit |

the sum of its potential energy and kinetic energy per unit mass | specific orbital energy |

the product of the gravitational constant and the mass | standard gravitational parameter |