Physics: Kinematics Flashcards

Question 1

What is Kinematics?

Accepted Answer

The branch of mechanics that describes how objects move, using position, velocity, acceleration and time, without asking what forces cause the motion.

Question 2

What is Position?

Accepted Answer

Where an object is located, measured from a chosen origin along a chosen positive direction, so it can be positive, negative or zero.

Question 3

What is Distance?

Accepted Answer

The total length of the path an object travels, counted without direction, so it is a scalar quantity that can never be negative.

Question 4

What is Displacement?

Accepted Answer

The straight-line change in position from start to finish, including direction, so it is a vector and may be smaller than the distance travelled.

Question 5

Define Scalar quantity.

Accepted Answer

A quantity described by size alone, with no direction, such as distance, speed, time or mass.

Question 6

Define Vector quantity.

Accepted Answer

A quantity that needs both a size and a direction to be fully described, such as displacement, velocity or acceleration.

Question 7

What is Speed?

Accepted Answer

How fast an object covers distance, found as distance divided by time; it has no direction and is measured in metres per second.

Question 8

What is Velocity?

Accepted Answer

The rate of change of position, including direction, so two objects at the same speed have different velocities if they move opposite ways.

Question 9

Define Average velocity.

Accepted Answer

Total displacement divided by the total time taken, which can be zero for a round trip even when the object moved quickly throughout.

Question 10

Define Instantaneous velocity.

Accepted Answer

The velocity of an object at one particular moment, equal to the slope of the tangent to its position–time graph at that instant.

Question 11

What is Acceleration?

Accepted Answer

The rate at which velocity changes, found as change in velocity divided by time and measured in metres per second squared (m/s²).

Question 12

What is Deceleration?

Accepted Answer

Acceleration that points opposite to the velocity, so the object slows down; its sign can be positive or negative depending on the chosen direction.

Question 13

Define Uniform (constant) acceleration.

Accepted Answer

Acceleration that stays the same size and direction over time, the condition under which the four kinematic equations are valid.

Question 14

Define Free fall.

Accepted Answer

Motion in which gravity is the only force acting, so every object accelerates downward at the same rate regardless of its mass.

Question 15

Define Acceleration due to gravity (g).

Accepted Answer

The acceleration of a freely falling object near Earth's surface, about 9.8 m/s² downward, often rounded to 10 m/s² for quick estimates.

Question 16

Define v = v₀ + at.

Accepted Answer

The kinematic equation linking final velocity, initial velocity, acceleration and time, used when displacement is neither given nor asked for.

Question 17

Define Δx = v₀t + ½at².

Accepted Answer

The kinematic equation giving displacement from initial velocity, acceleration and time, used when the final velocity is unknown and not needed.

Question 18

Define v² = v₀² + 2aΔx.

Accepted Answer

The kinematic equation connecting velocities, acceleration and displacement without time, which makes it the standard choice for braking-distance problems.

Question 19

Define Δx = ½(v₀ + v)t.

Accepted Answer

The kinematic equation finding displacement from the average of the initial and final velocities multiplied by time, valid only for constant acceleration.

Question 20

Define Big four (SUVAT) variables.

Accepted Answer

The five quantities in constant-acceleration problems: displacement, initial velocity, final velocity, acceleration and time; knowing any three lets you find the other two.

Question 21

Define Position–time graph.

Accepted Answer

A graph of position against time whose slope at any point equals the object's velocity at that moment.

Question 22

Define Velocity–time graph.

Accepted Answer

A graph of velocity against time whose slope gives acceleration and whose area down to the time axis gives displacement.

Question 23

Define Acceleration–time graph.

Accepted Answer

A graph of acceleration against time whose area down to the time axis equals the change in velocity over that interval.

Question 24

What is Projectile?

Accepted Answer

Any object launched into the air that then moves only under gravity, following a curved path once air resistance is ignored.

Question 25

What is Trajectory?

Accepted Answer

The path a projectile traces through space; with no air resistance it is a parabola, symmetric about its highest point.

Question 26

Define Independence of components.

Accepted Answer

The principle that horizontal and vertical motion of a projectile are analysed separately, linked only by sharing the same time of flight.

Question 27

What is Range?

Accepted Answer

The horizontal distance a projectile travels before returning to its launch height; on level ground without air it is greatest for a 45° launch.

Question 28

Define Time of flight.

Accepted Answer

The total time a projectile spends in the air, set entirely by its vertical motion: initial vertical velocity, launch height and g.

Question 29

Define Maximum height.

Accepted Answer

The highest point of a projectile's path, reached at the instant its vertical velocity component becomes zero.

Question 30

Define Frame of reference.

Accepted Answer

The viewpoint and coordinate system from which motion is measured; the same object can have different velocities in different frames.