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2.2 Moving at a constant speed:
Uniform motion
Suggest a method for When do objects move uniformly?
determining whether If an object travels equal distances within equal periods of time this
a car is moving motion is called uniform. For example, when a moving object leaves
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uniformly while you some kind of a trace behind as it is travelling (such as a car dripping oil),
are sitting in the back and we observe that the distance between the traces is equal, we can
infer that this object is moving uniformly. That means it is travelling with
seat and looking out of
a constant velocity.
the window.
What does velocity mean?
Velocity is a physical quantity that describes how fast an object is
moving in a specific direction. This means that velocity is a vector
quantity.
It is represented by symbol v. To calculate velocity (v), the total
displacement (S) is divided by total time taken (t) to travel the
displacement.
S
v =
t
The speedometer of this car shows nearly 120 km/h. What does this
mean? This means that a car travelling uniformly at this speed can cover
nearly 120 km in one hour.
The magnitude (value) of the velocity is very important. This is called
the speed. The speed is simply the value of an object’s velocity at
a specific point in time, and it is represented by s. As we are only
interested in the value, speed is a scalar quantity.
Speed is calculated in the same way as velocity. But this time, we
need the distance travelled (d) and the time taken to travel a specific
distance (t):
speed (s) = distance travelled (d) / time taken (t)
The direction of velocity is also important. The direction of the vector of
velocity shows the direction of motion of an object.
According to the International System of Units (SI), velocity is measured
in metres per second – m/s. In our daily lives we use other units, for
their convenience, such as kilometres per hour (km/h) or miles per
hour (mph).
REMEMBER! If the velocity of an object remains the same, we say that
the object moves uniformly. The trajectory of a uniform motion must be
in a straight line. This is called rectilinear uniform motion.
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