P2.1 Motion Flashcards
Define: acceleration
the change in velocity/change in time, measured in m/s2. IF THE SPEED AND/OR DIRECTION OF MOTION CHANGE…
… THE BODY IS ACCELERATING!
Define: average speed
total distance/total time, usually measured in m/s
Define: displacement
the distance from a point in a particular direction
Define: gradient
the degree of steepness of a graph at any point. Also called slope
Define: kinetic energy
the energy associated with a kinetic store
Define: kinetic store
energy in a kinetic store is associated with a moving object, calculated with: E = 1/2mv2
Define: scalar
a quantity that has magnitude (size) but no direction
Define: slope
slope measures the steepness of a line on a graph. Also called gradient
Define: ultrasound
sound with a frequency higher than human hearing (about 20 kHz), used in medicine, and for finding distances
Define: vector
a quantity that has direction as well as a magnitude (size)
Define: velocity
the speed in a particular direction, a vector
the speed equation
Speed=distance/time
Uniform speed
The speed stays constant for the whole journey.
➔ Speed calculated from distance and time is a single value.
Non uniform speed
NON-UNFORM
The speed changes and is not the same during the journey.
➔ Speed calculated from (total) distance and (total) time is
an average.
How many metres to a mile?
There are 1609m in a mile.
How many seconds to an hour?
There are 3600 seconds in an hour
Vectors vs Scalars
SCALARS ONLY HAVE MAGNITUDE
VECTORS HAVE BOTH
A MAGNITUDE AND A DIRECTION
Speed vs. Velocity
SPEED HAS ONLY MAGNITUDE.
VELOCITY HAS BOTH MAGNITUDE
AND DIRECTION
Speed vs. Velocity During Circular Motion
e speed of the plane stays the same. The velocity of the plane stays the same. The speed of the of the object stays the same whilst the velocity continually changes.
Distance vs. Displacement
DISTANCE
The length of the path travelled from A to B (size only = scalar).
DISPLACEMENT
The length of the shortest distance between 2 points
(size and direction = vector)
Explain why temperature is a scalar?
Temperature only has a size, no direction.
Adding Vectors
If vectors act in the same direction, you add them.
If vectors act in opposite directions, you subtract them.
You can only add/subtract vectors that either…
… act up and down
OR
… act left and right
How to calculate relative velocity of body A to body B?
take the difference between the velocities
How to calculate speed on a distant time graph?
The gradient of a line on a distance-time graph is equal to speed.
Displacement-Time Graphs
A displacement-time graph shows how the displacement of an object changes with time. The gradient of a displacement time graph equals velocity (not speed)
Thus, the gradient of a displacement time graph can be zero, positive or negative (unlike distance-time graph). A negative gradient would represent a negative velocity (so indicates a reverse in direction)
How to calculate the acceleration from a velocity time graph?
The gradient of a line on a velocity time graph is equal to acceleration
How to calculate displacement from a velocity time graph
The area under a velocity time graph is displacement
Equation of Motion that relates displacement, initial velocity, final velocity and time.
(v^2)– (u^2)= 2as
Kinetic Energy EQUATION
E = ½ x m x v^2
There are two ways to work out speed. If you divide the total distance travelled by the total time taken, you get the _____ speed. This _____ over the course of the journey. If you measure the speed over a very short time interval, you get the _____ speed. This _____ over the course of the journey. Speed and velocity are not the same thing. _____ is a measure of how fast you are moving, but _____ has a direction as well. Acceleration is a measure of how quickly the _____ is changing.
the average speed, stays the same
instantaneous speed, changes
speed, velocity
speed
Which four of the following statements are correct?
1) A skater travelling 100 metres in 20 seconds has an average speed of 50 m/s.
2) A snail travelling 1 metre in 100 seconds has an average speed of 0.01 m/s.
3) A sprinter travelling 100 metres in 10 seconds has an average speed of 10 m/s.
4) A car travelling 200 miles in 5 hours has an average speed of 40 mph.
5) A lorry travelling 100 miles in 2 hours has an average speed of 50 mph.
2, 3, 4, 5
A car that accelerates from 0 m/s to 30 m/s in 5 seconds has an acceleration of _____ m/s2.
6
A rocket that accelerates from 0 m/s to 100 m/s in 5 seconds has an acceleration of _____ m/s2.
20
A falling apple that accelerates from 0 m/s to 4 m/s in 0.4 seconds has an acceleration of _____ m/s2
A submarine that accelerates from 0 m/s to 2 m/s in 40 seconds has an acceleration of _____ m/s2
0.05 m/s2.
Sort these descriptions of distance–time (D/T) graphs and speed–time (S/T) graphs into three groups: those that appear as
a) a horizontal line
b) a diagonal line, or
c) neither.
1 - S/T graph: constant acceleration 2 - S/T graph: steady speed 3 - D/T graph: stationary object 4 - D/T graph: steady speed 5 - D/T graph: constant acceleration 6 - S/T graph: changing acceleration
a) 2, 3
b) 1, 4
c) 5, 6
Which three of the following statements are correct?
1) Something that goes 1 km in two minutes is going faster than something that goes the same distance in three minutes.
2) Something that goes 10 m in four seconds is going slower than something that goes the same distance in three seconds.
3) Something that goes 20 m in two seconds is going faster that something that goes 50 m in 10 seconds.
4) Something that goes 50 km in 30 minutes is going faster that something that goes 100 km in 45 minutes.
5) Something that goes 10 m in two seconds is going slower that something that goes the 50 m in 10 seconds.
1, 2, 3
a) A _____ m runner with an average speed of 5 m/s will run the distance in 40 seconds.
b) A runner who runs 26 miles in two hours has an average speed of _____ m/s.
c) A 400 m runner with an average speed of 8 m/s will run the distance in _____ seconds.
d) A 10 km runner with an average speed of 5 m/s will run the distance in _____ minutes and 20 seconds.
A) 200
B) 5.8
C) 50
D) 33 minutes and 20 seconds.
