solving word problems to solve a word problem, think: numbers, question, formula, label circle the...
TRANSCRIPT
Solving Word ProblemsTo solve a word problem, think:
numbers, question, formula, labelcircle the numbers, read the question,
write the formula and finally label the parts of the question that relate to the formula
Solving Word Problems – cont’dLet’s do a sample for density – follow the promptsA sample of substance X has a density of 5 g/ml
and a mass of 80 g. What is it’s volume?----------------------------------------------------------------numbersquestion formulalabelThen, solve the equation. Volume = 80 g / 5
g/mlVolume = 16 ml
Density = Mass / Volume Volume = Mass / Density
massdensity
MotionKinematics – branch of science which
describes motion [without describing the cause of the motion]
motion is measured as a change in positiondistances can be positive or negative
depends on the frame of reference
Frame of Referencethe frame of reference depends on the
observercompares speed and angles of movement
from the observer’s perspective and surroundings
explains the 75mph fly
SpeedSpeed – how rapidly an object changes
locationunits of distance divided by units of time
ex: miles per hour, kilometers per hour, centimeters per month, etc. d
distance
V
speed
t
time
Vspeed
=
d
distance
t
time
PracticeWhat is the speed of a runner that travels 250 m in 50 min?
5 m/min. 0.2 m/min. 12,500 m/min.How long does a trip of 3000 km take if you travel at 110 km/hr.?
330000 hr. 0.037 hr. ~27 hr.How far will a car traveling at 70km/hr. go in 2 hours?
360 km 140 km 0.4 km 2.5 km 0.04 kmWhat is the speed of a bike that travels 12 km in 30 min.?
360 km/hr 24 km/hr 0.4 km/hr 2.5 km/hr 0.04 km/hrAverage human walking speed is 5 km/hr. How far can you walk in
two hours?10 km 10 km/hr. 10 hr. 10 km•hr. [none]
Types of SpeedThree types of speed [distance divided by time]
average speedtotal distance divided by total time
instantaneous speedhow fast you’re going NOW
constant speedspeed that does not changenot really observed on earth – objects in
orbit, etc.
More PracticeWhat is the average speed of a cheetah that
sprints 100 m in 4 s?How about if it sprints 50 m in 2 s?
If a car moves with an average speed of 60 km/h for an hour, it will travel a distance of 60 km. (a) how far would it travel if it moved at this rate for 4 h? (b) for 10 h?
25 meters / second
25 meters / second
240 km
600 km
More Practice – cont’dIn addition to speedometer on the
dashboard of every car is an odometer, which records the distance traveled. If the initial reading is set at zero at the beginning of a trip and the reading is 40 km one half hour later, what has been your average speed?
Would it be possible to attain the average speed in previous example and never go faster than 80 km/h?
80 kilometers per hour
No – in order to have an average, need to have speeds higher and lower . If you had a constant speed, this would work, however, that is not realistic for typical scenarios.
PracticeWhich is a race car driver concerned with –
speed or velocity? a drag racer?The speedometer of a car moving to the east
reads 100 km/h. It passes another car that moves to the west at 100 km/h. Do both cars have the same speed?Do both cars have the same velocity?
During certain period of time, the speedometer of a car reads a constant 60 km/h. Does this indicate a constant speed or a constant velocity?
velocity [curved path]speed [going straight]
yes
no
constant speed – if it were velocity, there would be a direction listed