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Pearson Science 10 Physics feat. Motion, acceleration and momentum

Motion, Acceleration & Momentum
by

Philip De Zylva

on 10 May 2015

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Transcript of Pearson Science 10 Physics feat. Motion, acceleration and momentum

Motion, Forces & Energy
What is Motion?
Chapter Review
What is Acceleration?
Motion can be described by distance, speed, displacement, and velocity, where displacement and velocity also include direction.

Acceleration occurs whenever an object speeds up, slows down, or changes direction.

Inertia is the tendency of an object to resist a change in motion. Momentum is related to how hard it is to stop the object.

The law of conservation of momentum states than in a collision, the total momentum of the objects that collide is the same before and after the collision.
THE UNIVERSE
The Solar System
Earth
What is Motion?
A. All matter is constantly in
MOTION
.

B. Motion involves a
CHANGE
in position.

1. An object changes position relative to a
REFERENCE
point.

2.
DISTANCE
is the total length of the route an object travels when it moves.
(scalar quantity - size but not direction)

3.
DISPLACEMENT
includes distance and direction of the stopping point from the starting point.
(vector quantity - has a size and direction)

C.
SPEED - a measure of how quickly something moves.
1. The formula for

SPEED
can be written as: speed = distance/time. (OR v(speed) = d/t)
2. The units of speed are units of distance

divided by units of time; in SI units, speed is given as
METERS PER SECOND
(m/s).
Q: If a car has traveled 50 meters in 5 seconds; how fast was it going?
3. An object in motion can change
SPEED
many times as it moves from one point to another, speeding up or slowing down.
a.
AVERAGE SPEED
is the total distance traveled divided by the total time taken.
b. An object's speed at a particular moment in time is called
INSTANTANEOUS SPEED
.
c.
CONSTANT
speed occurs when an object travels at a steady rate with the same instantaneous speed for some period of time.
D. Motion can be
GRAPHED
on a distance-time graph with time plotted on the horizontal axis and distance plotted on the vertical axis.
CONSTANT SPEED INCREASE
CONSTANT SPEED
CONSTANT SPEED DECREASE
1. The steeper the line on a distance-time graph, the greater the
SPEED
.
2. A horizontal line on a distance-time graph indicates that no change in
POSITION
is occurring, and the speed is
ZERO
.
E.
VELOCITY
- speed of an object and its direction of motion; velocity changes if either, or both, of these changes.
Last Launch of Space Shuttle Endeavour
A.
ACCELERATION
- change in velocity divided by the time for the change to occur; it can include an object speeding up, slowing down, and/or changing direction.
B. Acceleration can be
CALCULATED
if you know how an object's velocity has changed during a given time period.
1. The formula for calculating
ACCELERATION
is:
Acceleration = final speed - initial speed / time or
a = (v-u)/t
.
can be rearranged to calc. final speed
v= u + at

a. The unit of acceleration is distance divided by time squared; in SI units, acceleration is given as
METERS PER SECOND SQUARED
(m/s2)
.

b. Acceleration is
POSITIVE
when an object speeds up and
NEGATIVE
when an object slows down.
Positive Acceleration (Speeding up)
No Acceleration
(Constant Speed)
Negative Acceleration (Slowing down)
2. Acceleration can be
GRAPHED
with speed on the vertical axis and time on the horizontal axis.
a. An object that is speeding up will have a line on a speed-time graph that slopes
UP & RIGHT
.

b. An object that is slowing down will have a line on a speed-time graph that slopes
DOWN & RIGHT
.

c. A horizontal line would indicate acceleration of
ZERO
, or constant speed.
What is Momentum?
A. The amount of matter in an object is its mass;
MOMENTUM
is the tendency of an object to resist a change in its motion.
Object filled with matter

B. MOMENTUM

- measure of how hard it is to stop an object; calculated as mass times velocity.
1. With
MOMENTUM
expressed as p, the equation can be written as: p = mv

2. Momentum
INCREASES
if the mass or velocity of the object increases.

3. Momentum has direction that is the same direction as its velocity.
C.
CONSERVATION OF MOMENTUM
- the total momentum of objects that collide with each other does not change.

1. There are
MANY
ways collisions can occur.

a. In one type, objects stick together and
MOVE
still stuck together.

b. In another type, two objects bounce off each other when they collide, and may transfer
MOMENTUM
from one to another.

2. In both cases, the
TOTAL
momentum of the objects that collide is the same before and after the collision.
Pre-quiz:

1. describe a situation in which a feather and a hammer would fall at the same rate

2. describe displacement

3. define force

4. state what quantity each of the following instruments measure
a) speedometer
b) trip meter

5. state what quantity is measured in each of the following units
a) m/s
b) kilometres
c) newtons

speed in km/h
speed in m/s
divide 3.6
multiply 3.6
Distance calculations

1. an object is travelling at 15 m/s for 10 seconds.

d = vt

2. an object is travelling at 20 m/s for 15 minutes. How far does it travel?

3. Trinh rides her bike with a constant speed of 5m/s. It takes her 3 minutes to get to the milk bar. Calculate how far away it is.

4. While Trinh is riding, a toddler runs onto the road ahead. If Trinh took 0.5 secs to react, how far does she travel before hitting the road?
Speed calculations

1. convert the following speeds into km/h
a) 3m/s
b) 12.5 m/s

2. convert the following speeds into m/s
a) 54 km/h
b) 16.2 km/h

3. Theo spent 8 hours travelling 400 km from his home in Bundaberg to visit his sister in Toowoomba. Calculate Theo's average speed for the journey.

C. Velocity
- how displacement changes with time
1. The formula for
Velocity

can be written as: velocity = distplacement/time. (OR v(speed) = d/t)
2. The units of speed are units of distance

divided by units of time; in SI units, speed is given as
METERS PER SECOND
(m/s).
Q: If a car has traveled 50 meters in 5 seconds; how fast was it going?
average acceleration and final speed

1. a car speeds up to 60 km/h from rest in 5 seconds. calculate its average acceleration (km/h/s)

2. a train initially travelling at 30 km/h accelerates at a constant rate of 2 km/h/s for 30 seconds. Calculate it's final speed.

3. a car brakes from a speed of 30 m's decelerating at a rate of -5 m's. Calculate time taken to stop and eventual speed.


fill in the missing values
use the acceleration formula to calc. missing values
Practice makes perfect
acceleration due to gravity
a falling object accelerates towards earth because of the force of gravity.
acceleration due to gravity is 9.8 m/s2 (1 g)
speed of object increases by 9.8 m/s (or 36km/h) for every second it falls
G-force
air resistance
- the friction between air and a falling object
terminal velocity
- the final velocity
Human tolerance
depends on how big the force, duration, direction, part of body they affect.
can handle horizontal better then vertical
forces experienced in vertical drop are dangerous as blood flow to the brain can be disrupted
body can withstand momentary force but longer durations can be deadly
vertical dives up to 300 km/h

as it pulls out of a dive,
the falcon can withstand
forces up to 25g!
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