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.
How do you calculate the distance/displacement from a speed/velocity - time graph?
The distance/displacement is the area under the the line on a speed/velocity -time graph.
What type of quantity is acceleration?
Vector quantity so can have a positive or negative value
What is the relationship between the steepness of the line and the speed?
The steeper the line is, the faster the object is travelling
What does a levelling of curve mean on a distance-time graph?
A levelling off curve means it’s slowing down
How do you work out the speed if a distance-time graph is curved?
If the graph is curved, to find the speed at a certain time you need to draw a tangent to the curve at that point and then find the gradient of the tangent.
What does a curve mean on a velocity-time graph?
A curve means changing acceleration
What is the equation for kinetic energy?
Kinetic energy (J) = 0.5 x mass (kg) x (speed (m/s))^2
What do the uphill (/) sections on a velocity time graph show?
It shows constant acceleration.
What is the difference between a distance-time graph and a displacement-time graph?
A distance-time graph shows the total distance travelled.
If you plot a displacement-time graph, then the gradient can be positive, zero or negative. The gradient of the graph is the velocity, so it has direction as well as magnitude.
What do the flat sections show on the velocity-time graph?
The flat sections represent steady velocity
What do curves on distance-time graph mean?
Curves represent acceleration
What is Newton’s third law?
For every action there is an equal and opposite reaction
When two objects interact, the forces they exert on each other are equal and opposite
Define inertia
Inertia is the ensure of how difficult it is to change an object’s velocity.
Give examples of non-contact forces
Electrostatics
Magnetism
Gravity
Nuclear
What are non-contact forces?
Non-contact forces are fries between two object’s that aren’t touching
What are contact forces?
A contact force is when two objects are touching
Give examples of contact forces
Friction Drag/air resistance Normal contact force Upthrust (buoyancy) Tension
Define force
A force is a push or pull that can either change the movement, speed or shape of an object.
What is the mechanism that produces friction on a sliding box?
The atoms that make up the surfaces interact when rough surfaces slide over each other
What is the mechanism that produces drag on a falling leaf?
The particles of the liquid or gas collide with the object and the object pushes them away
What is the mechanism that produces normal contact force of the ground acting on an elephant?
Solid objects deform slightly when you exert a force on them. The bonds between the particles are compressed.
What is the mechanism that produces up thrust on a floating boat?
Gravity produces pressure differences in a fluid. The pressure produces a net upwards force.
What is the mechanism that produces tension in the chord of a bungee jumper
Solid objects slightly when you exert a force on them. The bonds between the particles are stretched.
Define a free body diagram
A free body diagram is a diagram that shows the forces acting on a single object.
