Motion – continuous change of position with
respect to a certain reference point.
Distance – refers to the total length of path
(scalar quantity)
Displacement – the straight-line distance
between the starting and end points (vector
quantity)
Speed is the rate at which an object moves
Speed = distance/time
Vs = d/t
where Vs = speed
d = distance
t = time
Example, if the cyclist moves 30 km in 2h, his
speed is Vs = 30 km/2h = 15 km/h
Vave = (V1 + V2 + … Vn)/n
Instantaneous spped – the speed measured at a
particular time or instant
Velocity is defined as speed plus direction. It is
a vector quantity
Example: 80 km/h, northward
In symbols, v = d/t
where v = velocity
d = displacement
t = elapsed time
Speed and velocity are often used
interchangeably; however, there is a clear
distinction between these two concepts.
Speed makes use of distance while velocity
makes use of displacement. Because distance
and displacement are different quantities, the
magnitude of velocity will sometimes be
different from that of speed. Speed and
velocity will be equal in magnitude if the
distance and displacement are also equal in
magnitude.
A car travels a distance of 40 km from Manila
to a town in Laguna (south). Assume that the
car traveled in constant speed. What is its
average speed (in km/h) if traveling time is
from 7:00AM to 7:30 AM? Its average
velocity (km/h)? Suppose that after a
business talk with a friend, the driver of the
car drives straight back to Manila from
11:55AM to 12:20 PM. What was the car’s
average speed (km/h) during the round trip?
Its average velocity (km/h)
Given:
d1 = 40 km (1st trip)
d2 = +40 km (return trip)
t1 = 30 mins (1st trip)
t2 = 25 min (return trip)
a. Speed = d/t = 40km/30 min = 1.3
km/min
= 78km/h
b.
c.
Average velocity = -40km/0.5hr) = 78km/h from Manila to Laguna or southward
Ave speed for the round trip = total distance
during the round trip/total time spent for
the roundtrip
= (d1 + d2)/(t1 + t2)
= (40km + 40km)/(30 mins + 25 mins)
= 90km/h
d.
The average velocity, v, for the round trip =
total displacement for the round trip / time
it takes for the total displacement for the
roundtrip
= [+40km + (-40km)] / 30min + 25 min
= 0/50 mins = 0
1.
2.
3.
At the start of a trip, a car’s speedometer read
34,627 km, while at the end, it read 35,118 km.
If the trip took 8hours, what was the car’s
average speed assuming that the car moved at a
constant rate?
An airplane flies westward at a velocity of 220
km/h. If the wind is blowing southward with a
velocity of 20 km/h, what is the resultant
velocity of the airplane?
A truck’s velocity was 60km/h, south. How far
did it go after 15 mins? What was its total
displacement?
Acceleration – change in velocity for every unit
of time
a = (vf – vi)/t
1-3. Choose the motion from a to d that
matches with each scenario from the
following situations
a. The car speeds up c. The car
decelerates
b. Velocity is changed d. No fuel is
consumed
1. Which of the above happens when a driver
steps on the accelerator?
2. Which of the above happens when a driver
steps on the brake?
3. Which of the given situations happen when a
driver turns around a rotunda?
4.
5.
6.
7.
8.
A car traveled at 88 km/h for 5 hours. How
far did it travel?
Mark walked 5 km/h. How long did it take
him to travel 15 km?
A ferryboat travels 90km in 45 mins. What
is the average speed of the boat?
A car has an initial velocity of 40 m/s. It
stops over a distance of 120 m when the
brakes are applied. How long does it take
for the car to stop? What is the car’s
deceleration?
If it takes you half an hour to go 1 km across
town, then what is your average speed?