Chapter 1 - Kinematics Flashcards
Kinematics
Study of motion without looking at forces causing the motion
Terms used to describe motion (5)
Distance, displacement, speed, velocity, acceleration
Distance
Actual path followed by a moving object
Scalar quantity measured in metres (m)
Displacement
Shortest distance between 2 points (straight line), distance travelled in a particular direction
Vector quantity measured in (m)
Motion in a circle
Distance around full circle is 2πr
Displacement around full circle is 0
Velocity is 0
Distance from opposite halves is πr
Displacement is 2r
Average Speed
Scalar quantity measured in ms-1
Usually changes unless an object is moving at a constant speed, so we take an average
Velocity
Vector quantity measured in ms-1
Acceleration
Rate of flow of velocity
Vector quantity measured in ms-2
Circular motion
movement of an object along the circumference of a circle or rotation
along a circular path. This motion occurs when the vectors of velocity and acceleration are
constantly perpendicular.
Projectile motion
form of motion in which an object or particle (called a projectile) is thrown near the earth’s surface, and it moves along a curved path under the action of gravity only. The only force of significance that acts on the object is gravity, which acts downward to cause a downward acceleration.
Terminal velocity
highest velocity attainable by an object as it falls through a fluid such as air or oil.
Newton’s laws of motion
three physical laws which provide relationships between the forces acting on a body and the motion of the body.
Newtons 1st law
States that an object in motion continues to move with uniform velocity, an object at rest stays at rest, unless the object is acted upon by a resultant force
Inertia
tendency of an object to resist changes in its state of motion
What can be deduced from Newtons 1st law (3)
Inertia - tendency of an object to resist changes in its state of motion
An object can move without forces acting on it
If an object is at rest/moving with constant velocity then all forces acting in any direction have a resultant of 0
Instantaneous speed
Speed of an object measured over a very short period of time
Resultant
Single vector formed by adding together 2 or more vectors
Laboratory measurements of acceleration (3)
Light gates - computer records first interrupt as card passes through the beam of the light gate. Length of interrupt determines the initial speed. Same is done for second light gate. Computer also records time between the measurements. Calculations can now be done to determine the acceleration
Ticker timer - tape divided into sections (5 dots per section), interval between each adjacent dot is 0.02s therefore each section represents 0.10s. Length of each section gives displacement in 0.10s
Motion sensor
Uniform acceleration
When the change in velocity of an object is the same in the same time period
Non-uniform acceleration
When the velocity of an object changes by different amounts in the same period of time
When are SUVAT equations used
Uniform acceleration
What can help you visualise the effect of grain a moving object
A multi-flash photo, it shows the object at equal intervals of time
Free fall
When an object accelerates due to gravity in the absence of any other forces such as air resistance
Laboratory measurements of g (gravity) (3)
Electronic timer
Ticker-timer
Light gate
Measuring g using an electronic timer
Steel ball bearing is held by an electromagnet. When current to the magnet is switched off, the ball begins to fall and an electronic timer starts. The ball falls through a trap door, breaking the circuit and stopping the timer. Take several measurements of t for different values of h.
Measuring g using a ticker-timer
A weight attached to tape falls, pulling the tape through a ticker timer. This is not an ideal method due to the friction between the tape and the ticker timer
Component
The effect of a vector along a particular direction
