can u explain this.. it's physics and math together?

Question

what is Acceleration phase: (how do we use it and when)
what is Deceleration phase:(how do we use it and when)
thanx!

Answer 1

Acceleration means any change in velocity, including speeding up, slowing down, or changing direction. However, it is often used to specifically mean an increase in velocity. Deceleration is the specific case of acceleration where either the absolute value of velocity decreases, or when velocity decreases overall (including increasing magnitude at negative values).

Answer 2

Acceleration and deceleration are the same thing except deceleration is acceleration with a - (negative) sign. For example, if the speed is increasing by 3 m/s per second, it is acceleration but of it is decreasing by 3 m/s per second it is deceleration or you could also say that the acceleration is -3 m/s per second.

Acceleration is given by

acceleration a = (v-u)/t

where v = final velocity
and u = starting velocity
and t = time taken

Please remember that even a change in direction constitutes acceleration, For example, if an object is moving at 20 m/s in the northword direction and then it changes direction towards east but the speed remains 20 m/s, the body is said to have undergone acceleration. If you notice what happens when you are sitting in a car that changes direction even though the speedometer needle points at say 40 mph, you still feel like thrown on to one side by the centrifugal force. This force is also referred to as the g force and it occurs due to change in velocity (not change in speed). Where change in velocity is due to change in direction. Read about angular velocity to understand this concept.

Answer 3

Let us take an every day example of you and your dad going to school in his car. Both of you sit in the car, fasten the seat belts (very important for your safety as you will shortly see) and dad starts the engine, engages the gear and the car starts moving. Well, congratulations! you are in the acceleration phase! You started moving from rest and there is a change in velocity! While the word acceleration refers to any change in velocity (positive or negative), people normally reserve the word acceleration to mean a positive change in velocity, an increase.

OK, the car has touched the speed limit and since your dad is a careful driver and a responsible citizen, he sticks to the maximum speed limit. So, the car is now going at a constant speed and if the road is straight, constant velocity. The acceleration is now zero.

Your school is ahead (may be a hundred yards or so) and your dad is a good scientist and wants to conserve the fuel and minimise the carbon dioxide emission etc. from the car. He knows the road is level and from earlier experience he knows that if he cuts the engine and puts the car in neutral gear, it will go that distance before stopping. Congratulations again for decelerating (reducing the velocity) by using the friction between the road and the tyres. The car slows down and stops in front of your school. You unfasten your seat belt, give a kiss to your dad and get down from the car and run to meet your friends waiting for you.

While going in the car, your dad may need to apply the brakes suddenly to avoid hitting a stray dog or rabbit etc. running across the road and at that time, there will be sudden deceleration of the car. Without the seat belt, you will continue to move at the higher speed and will hit the dashboard and get hurt. Similarly, if your dad is in a hurry and guns the engine and makes the car jump forward, you will be pushed back into your seat. Or you might have experienced that in an aircraft during take off and landing. Going up and down the lift.

In all these cases, sudden changes in velocity are present as you can see now.

Answer 4

Acceleration is used to measure the change of velocity. For example, if the existing velocity of a car is 5m/s [v1] and it is going to be 10m/s [v2] after 1s [t1], then the acceleration is a = (v2 - v1) / t1 = (10-5)/1 = 5m^2/s. Based on this result, we understand that the car is speeding up.

Deceleration is actually the opposite side of acceleration. For example, when the speed of the car is up to 10m/s now, and then stop [0 = v3] at 1s [t2]. The acceleration is a = (v3 - v2) / t 2 = (0 - 10)/1 = -10m^2/s. Based on this result, because the result of this acceleration is negative, we understand that the car is slowing down. And, we call this deceleration = 10m^2/s (acceleration = -10m^2/s).

Based on our calculation, we mainly calcuate everything at acceleration. Therefore, when you see the question at deceleration, you just turn them into acceleration with negative.

I hope it can help you understanding the meaning of acceleration and deceleration.

Answer 5

If an object is thrown up with certain speed, its speed decreases as it goes up.
The rate of change of velocity is 10m/ s^2. In every second its velocity decreases by 10m/s.

Therefore the acceleration is ─10m/s^2.

The deceleration is +10m/s^2.

If the object comes down the acceleration is positive and is = +10m/s^2.

The deceleration in this case is ─10m/s^2.