Forces Flashcards
How do you measure the time of a falling object?
Light gates
What affects the precision and accuracy of time measurements?
Reaction time
How does a light gate work?
A timer starts and stops when an object interrupts a light beam
What is an advantage of using a light gate?
You can measure very short periods of time
Give a way of measuring distance accurately
Ultrasound
What does ultrasound use?
High-frequency sound waves
How does ultrasound work?
The device measures the time taken for a pulse to travel there and back. It uses this value and the speed of the pulse to measure the distance.
The equation for uniform motion speed
Average speed (m/s) = total distance (m) // total time (s)
What is non-uniform motion
Motion where speed changes
SI units
Metre and seconds
Metres in a mile
1609m
How do you convert between units?
With the speed equation
What is the difference between a vector and a scalar?
Vectors have magnitude and direction, scalars only have a magnitude
An example of a vector
Force, where the length of the arrow shows the magnitude (size)and the direction shows the direction
An example of a scalar
Measurement made with a stopwatch e.g. magnitude 10s
Difference between displacement and distance
Distance is total distance travelled while displacement is the distance from the starting point
What is the difference between speed and velocity?
Speed is scalar, velocity is vector
Explain positive and negative velocity
A car traveling to the west has a velocity of -40mph while a car travelling to the east has a velocity of +40mph
What is acceleration?
Change in velocity per second
How do you accelerate?
You go from one speed to another
Uniform acceleration
Acceleration does not change
Formula for acceleration
Acceleration (m/s2) = change in velocity (m/s) // time (s)
Units for acceleration
m/s2
What does a graph of distance against time mean?
- A diagonal straight line means moving at constant speed because the gradient does not change
- A horizontal line means the object is not moving
- The steeper the line the faster the speed
How is a distance-time graph different from a displacement-time graph?
Distance-time shows total distance travelled.
In a displacement-time graph, the gradient can be positive, negative or zero.
The gradient of the displacement-time graph is velocity.
Time against x-axis
Rate of change with time
Gradient of a velocity-time graph
Vector acceleration
Area under a speed-time graph
Distance
Area under velocity-time graph
Displacement
What is the equation of motion used for?
For objects with a constant acceleration
Equation of motion
(Final velocity (m/s))2 - (initial velocity m/s))2 = 2 x acceleration (m/s2) x distance (m)
