Chapter 2 Kinematics Flashcards
1
Q
Scalar quantities
A
Remember scalar quantities only have a magnitude (size)
Distance: the total length between two points
-Speed: the total distance travelled per unit of time
2
Q
Vector quantities
A
- Remember vector quantities have both magnitude and direction
- Displacement: the distance of an object from a fixed point in a specified direction
- Velocity: the rate of change of displacement of an object
- Acceleration: the rate of change of velocity of an object
3
Q
On a displacement-time graph…
A
- slope equals velocity
- -the y-intercept equals the initial displacement
- a straight line represents a constant velocity
- -a curved line represents an acceleration
- a positive slope represents motion in the positive direction
- -a negative slope represents motion in the negative direction
- a zero slope (horizontal line) represents a state of rest
- -the area under the curve is meaningless
4
Q
On an acceleration-time graph…
A
- slope is meaningless
- the y-intercept equals the initial acceleration
- a zero slope (horizontal line) represents an object undergoing constant acceleration
- the area under the curve equals the change in velocity
5
Q
Area under a Velocity-Time Graph
A
- Velocity-time graphs show the speed and direction of an object in motion over a specific period of time
- -The area under a velocity-time graph is equal to the displacement of a moving object
- displacement = area under a velocity-time graph
6
Q
Gradient of a Displacement-Time Graph
A
- Displacement-time graphs show the changing position of an object in motion
- They also show whether an object is moving forwards (positive displacement) or backwards (negative displacement)
- A negative gradient = a negative velocity (the object is moving backwards)
- -The gradient (slope) of a displacement-time graph is equal to velocity
- The greater the slope, the greater the velocity
7
Q
Gradient of a Velocity-Time Graph
A
- Acceleration is any change in the velocity of an object in a given time
- As velocity is a vector quantity, this means that if the speed of an object changes, or its direction changes, then it is accelerating
- An object that slows down tends to be described as ‘decelerating’
- The gradient of a velocity-time graph is equal to acceleration
8
Q
Deriving Kinematic Equations of Motion
A
- The kinematic equations of motion are a set of four equations which can describe any object moving with constant acceleration
- They relate the five variables:
- s = displacement
- u = initial velocity
- v = final velocity
- a = acceleration
- t = time interval
9
Q
equations of motion
A
- v = u + at
- v2= u2 + 2as
- s = ut + 1/2at2
- s= (u+v/2)xt
10
Q
Solving Problems with Kinematic Equations
A
- Write out the variables that are given in the question, both known and unknown, and use the context of the question to deduce any quantities that aren’t explicitly given
- e.g. for vertical motion a = ± 9.81 m s–2, an object which starts or finishes at rest will have u = 0 or v = 0
- Choose the equation which contains the quantities you have listed
- e.g. the equation that links s, u, a and t is s = ut + ½at2
- Convert any units to SI units and then insert the quantities into the equation and rearrange algebraically to determine the answer
11
Q
Systematic error:
A
- Systematic Error
- *Faults in the apparatus or experimental method. Affects accuracy.**
12
Q
Random error
A
- Random Error
- *Unpredictable changes in an experiment causing one measurement to differ slightly from the next. Affects precision.**
13
Q
Projectile Motion
A
- The trajectory of an object undergoing projectile motion consists of a vertical component and a horizontal component
- These need to be evaluated separately
- Some key terms to know, and how to calculate them, are:
- Time of flight: how long the projectile is in the air
- Maximum height attained: the height at which the projectile is momentarily at rest
- Range: the horizontal distance travelled by the projectile
14
Q
Remember:
A
- the only force acting on the projectile, after it has been released, is gravity
-
There are three possible scenarios for projectile motion:
- Vertical projection
- Horizontal projection
- Projection at an angle
15
Q
Km/h to m/s
A
Divide km/h value by 3.6