An object moving at a constant velocity will have zero acceleration.

An object moving at a constant speed can still have acceleration if it's changing its direction.

We sometimes refer to a decrease in velocity (a slowing down) as an acceleration.

Acceleration is:

- Rate at which velocity changes
- Vector quantity, with magnitude and direction

If velocity is increasing, the acceleration is in the same direction as the velocity as depicted below:

How about a car on the circular track having a constant speed (see below), but with a changing velocity every second.

Question: Explain why.

Solution:

Acceleration has to do with the change of velocity's direction and/or magnitude.

If an object is not changing its velocity, then the object is not accelerating.

this mean the car is accelerating.

As per the above table 1, since the velocity is changing by a constant amount each second,

the acceleration is said to be constant.

Question: which one of them has constant acceleration?

Answer:

To calculate the acceleration, we need to measure the initial velocity v

and the final velocity of the object v

The Accelaration formula is as follows:

Acceleration a = Change in Velocity / Time Interval = Δv / Δt

Example 2: The car in the figure below moves in constant acceleration from an initial speed of 22 m/s to a final speed of 32 m/s.

If this increase of velocity took 5 seconds, calculate the car acceleration.

Solution:

a = Δv / Δt = 10 m/s / 5 s = 2 m/s

Question 2: Show that the acceleration of a speed boat is 25 m/s

Solution:

Answer:

Hence distance = ½×a×t

a = (40 m/s) / 8s = (5 m/s)/s = 5 m/s^{2} |

fall to earth at the same rate with the same acceleration and is called acceleration due to gravity.

Such bodies are in a state of free fall.

Acceleration due to Gravity (g) = 9.80 m/s

The instantaneous speed (or velocity) v of an object falling from rest after a time t is v = gt

The equation indicates that the speed increases by 9.8 m/s in each second of fall.

The table below shows how the speed (or velocity) changes each second. In here, we rounded off g to 10 m/s

Question: Calculate the velocity before the ball crashes to the ground. (g=10m/s

Solution:

Assume gravity g = 10m/s

Velocity is: V=g × t = 10m/s

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Date of last modification: Summer , 2019