# P2.1 Motion Flashcards

• Created by: xmariamx_
• Created on: 07-04-18 18:58
How do you measure distance and time in the lab?
You use a ruler or measuring tape to measure distance and light gates to measure time.
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What are light gates?
Light gates- measures the time of how long an object interrupts a light beam.
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What is another method of measuring distance?
Ultrasound (high frequency waves) can be used to measure distance. It measures the time taken for a pulse to travel there and back. It uses this value and the speed of the pulse to work out the distance.
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How do you calculate distance?
Distance travelled (m) = speed (m/s) x time (s)
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How do you calculate speed?
Average speed (m/s) = total distance (m) / total time (s)
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How many metres make up a kilometre?
1000m
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How many metres make up a mile?
1609m
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How many seconds make up an hour?
3600s
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Advantages - less likely for human error to occur Disadvantages - only measure short amounts of time, not long
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Advantages - can measure longer distances Disadvantages - requires good reaction time
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Uniform motion
In uniform motion speed does not change
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State the two types of motion
Horizontal and vertical
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What is the difference between a vector and a scalar?
A scalar quantity has only magnitude. A vector quantity has both magnitude and direction.
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Vectors
Represented with arrows. Length shows the magnitude, the direction shows the direction.
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Scalar
It has a magnitude, but no direction. Measurement made with a stop clock.
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What is displacement?
Displacement - the distance from a point in a particular direction
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What is the difference between speed and velocity?
Speed is a scalar quantity, 15 m/s is a measurement of speed. Velocity is a vector quantity. It has a direction as well as a magnitude. Example: 15 m/s A velocity is positive if it moves from left to right, and negative if from right to left.
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How do you add vector quantities?
You can add vector quantities but you must take into account the + or - sign. +20 m/s (right) + +20 m/s (right) = +40 m/s
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What is acceleration?
A measure of how quickly an objects velocity changes. You use + or - to show the direction of motion. Uniform acceleration means the acceleration does not change.
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What is the equation of uniform acceleration?
Uniform acceleration = change in velocity (m/s) / time (s)
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Negative acceleration or deceleration?
It is better to say negative acceleration rather than deceleration.
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What is the equation for acceleration?
Acceleration (m/s^2) = final velocity - initial velocity / time (s)
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What is the acceleration due to gravity?
The acceleration due to gravity is 9.81 m/s^2 or 10 m/s^2
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What is another way of thinking about acceleration?
Another way of thinking about this acceleration is that when something is falling vertically, during each second its downwards velocity increases by about 10 m/s
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What does a curved slope represent in a distance-time graph?
Curved slope = object moving at non-uniform speed
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What does a straight slope represent in a distance-time graph?
Straight slope = object moving at uniform speed
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What does no slope represent in a distance-time graph?
No slope = object stationary
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What does a graph of distance against time mean?
The gradient of a distance-time graph represents the speed of an object
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From the graph can we tell how fast the object is travelling?
Yes, the steeper the line, the faster the object is travelling
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How do you calculate speed from a distance-time graph?
Step 1: Draw a right angled triangle under the line Step 2: Find the change in distance and the change in time Step 3: Use the equation for speed
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What is the equation for speed?
Speed = change in distance / time
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How is a distance-time graph different from a displacement-time graph?
A distance-time graph shows the total distance travelled. A displacement-time graph gives the velocity of the object and a particular time (has a direction as well as a magnitude)
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How do you calculate velocity from a distance-time graph?
Step 1: Draw a right angled triangle under the line Step 2: Find the change in displacement and change in time Step 3: Use the equation to find the answer
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What is the equation for velocity?
Velocity = change in displacement / time
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What can you deduce from the gradient of a velocity-time graph?
The gradient of a velocity-time graph tells you about a rate of change with time. The rate of change of speed or velocity with time tells you the acceleration.
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What is the rate of change?
How much one variable changes when another changes. Usually refers to the change of a variable with time.
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How do you calculate acceleration from a velocity -time graph?
Step 1: Find the change in speed and time Step 2: Use the equation for acceleration
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What is the equation for acceleration?
Acceleration = change in velocity/ change in time
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What does negative accelreation show?
It shows the object is slowing down
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What does positive acceleration show?
It shows the object is speeding up
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If the object is moving in the same direction all the time...
the velocity is positive
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If the direction changes...
the velocity is positive first and then negative (or vice versa)
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How do you calculate displacement from a velocity-time graphs?
Step 1: Work out the distance represented by each square Step 2: Count the number of squares and multiply the distance per square by the number of squares to find the displacement. And together parts of squares to make whole squares
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The distance travelled is...
the area under a speed-time graph
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The displacement is...
area under a velocity-time graph
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What is the equation of motion?
(final velocity (m/s))^2 = (initial velocity (m/s))^2 = 2 x acceleration (m/s^2) x distance (m)
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How do you calculate velocity using the equation of motion?
Step 1: write what you know - initial velocity, acceleration, distance Step 2: make final velocity the subject Step 3: substitute the values in (2 s.f.)
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How do you calculate kinetic energy?
Step 1: write what you know (use standard units) - mass, speed Step 2: use the equation and substitute the values in
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What is the equation for kinetic energy?
kinetic energy (j) = 0.5 x mass (kg) x (speed (m/s))^2
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## Other cards in this set

### Card 2

#### Front

What are light gates?

#### Back

Light gates- measures the time of how long an object interrupts a light beam.

### Card 3

#### Front

What is another method of measuring distance?

### Card 4

#### Front

How do you calculate distance?

### Card 5

#### Front

How do you calculate speed?