2. What exactly is speed?
In everyday use and in kinematics, the speed of an object is
the magnitude of the change of its position; it is thus a scalar
quantity.The average speed of an object in an interval of time
is the distance travelled by the object divided by the duration
of the interval;the instantaneous speed is the limit of the
average speed as the duration of the time interval
approaches zero.
3. How to we measure speed?
Speed has the dimensions of distance divided by time. The
SI unit of speed is the metre per second, but the most
common unit of speed in everyday usage is the kilometre per
hour or, in the US and the UK, miles per hour. For air and
marine travel the knot is commonly used.
4. The change of speed
Acceleration is defined strictly as the time rate
of change of velocity vector. Deceleration, on
the other hand, is acceleration that causes
reduction in "speed".
Reminder:Deceleration is not opposite of acceleration.
It is certainly not negative time rate of change of velocity.
5. What is the average acceleration of a car?
The average rate of
acceleration of all the
ordinary cars I found was
between 3 and 4 m/s2.
6. What is the average acceleration of a cheetah?
A cheetah can go from 0 to
60 miles an hour in only three
seconds(About 9 m/s2 in
average)
7. What is the average acceleration of an athlete？
The average acceleration
of an athlete (during this
interval) is approximately
around 3.09 m/s2
