P2 Flashcards
What is the speed distance time formula?
distance travelled (m) = speed (m/s) x time (s)
How do you convert from mph to m/s?
Step 1) convert the miles to metres (1609 m/mile)
Step 2) convert hours to seconds (3600 s/hour)
Step 3) Use the equation speed distance time to find the speed
Define uniform-motion.
It is when the motion is at a constant speed so the speed doesn’t change.
List one thing we can use to measure the time it takes for an object to travel a specific distance.
A stopwatch
A light gate
Why do some scientists use ultrasound to measure distance?
An ultrasound measures the time taken for a pulse to travel there and back, which means it is more efficient and accurate as you can’t make a human error and it can record long distances.
Define acceleration
The change in velocity per second
Suggest why light gates are more accurate than stopwatches.
They are more accurate than stopwatches because the reaction time of the person can affect the precision of the measurement. Light gates use a timer which starts and stops when an object interrupts a light-beam. So you can measure very short periods more accurately than stopwatches.
Light gates minimise/eliminate errors
Convert 50 mph to m/s.
50 miles = 50 miles x 1609 m/mile
= 80450 m
1 hour = 3600 s
Speed= distance / time
= 80450 / 3600
= 22.35 m/s (2dp)
When all the forces acting on an abject is not equal…
…the object will be accelerating
What is the difference between a scalar quantity and a vector quantity?
The difference is that a vector quantity is a measurement that has a magnitude (size) and direction whereas a scalar quantity only has a magnitude.
What’s the difference between distance and displacement?
Distance= the total amount of meters travelled Displacement = the total amount of meters you ended up with compared to where you started
What does a horizontal line on a distance-time graph mean?
A horizontal line means that the object is not moving
Equation to calculate acceleration
acceleration (m/s^2) = change in velocity (m/s) / time (s)
What’s the difference between speed and velocity?
Speed is a scalar quantity so it doesn’t have direction whereas vector is a vector quantity so it is the speed with a direction.
List one thing we can use to measure the distance travelled by an object.
A ruler
An ultrasound
An object is accelerating, the moment…
…its speed changes
…its direction changes
OR
…both
What do the downhill () sections on a velocity time graph show?
It shows constant deceleration
Write the Equation of motion
(Final velocity)^2 (m/s)^2 - (initial velocity)^2 (m/s)^2
= 2 x acceleration (m/s)^2 x distance (m)
v^2 - u^2 = 2 x a x d
What does a graph of distance against time tell you?
It tells you about the speed of an object not its journey.
When all the forces acting on an object are equal/balanced…
…the motion of an object will be uniform (Fnet = 0N)
What is speed equal to on a distance time graph?
It is equal to the gradient (slope) of the graph.
In a velocity-time graph what is the gradient equal to?
The gradient is equal to acceleration (magnitude and direction)
What does a straight line on a distance-time graph mean ?
A straight line means an object’s speed is constant because the gradient doesn’t change
What does a steepening curve mean in a distance-time graph?
A steepening curve means it’s speeding up.
