What do you understand by the term acceleration? What is meant by its

1.	What do you understand by the term acceleration? What is meant by its being positive or negative? Explain with example. Write its SI units?
Answer» Answer: Acceleration: ➤ The rate of change of velocity of a body is called acceleration. Positive acceleration: ➤ If the velocity of a body is *INCREASING* with respect to time, then the acceleration is said to be positive. For EXAMPLE: A cyclist moving through a busy street does not have a uniform velocity. The velocity of cyclist may change in magnitude, the direction or both. In such a case the cyclist is said to have an accelerated motion, which is positive as it is moving in forward direction or the velocity of the body is increasing with respect to time. Negative acceleration: ➤ If the velocity of the body is *decreasing* with respect to time, the acceleration is said to be negative. It is also called *deceleration* or *retardation. For* example: When we throw the ball UPWARDS i.e, in the upward direction, then the negative acceleration acts on it. As the velocity of an object is negative. Therefore the acceleration is negative. Unit of acceleration: In SI system it is expressed in m/s². N.B - It must be remembered that acceleration is a *vector quantity, as it is expressed in magnitude and direction. It is generally represented by letter 'a'.* Give one similarity and one dissimilarity between the GRAPHS: Ans. Similarity: Both the graphs show *uniform acceleration* that is the body describes equal change in velocity in equal intervals of time. Dissimilarity: In the first graph, the object starts from the rest. Therefore the initial velocity is zero, v = 0. In the second graph, the object does not start from rest, as the object possesses some velocity when it starts that is it possesses some initial velocity, v ≠ 0. _______________________________

What do you understand by the term acceleration? What is meant by its being positive or negative? Explain with example. Write its SI units?

Answer»

Answer:

Acceleration:

➤ The rate of change of velocity of a body is called acceleration.

Positive acceleration:

➤ If the velocity of a body is INCREASING with respect to time, then the acceleration is said to be positive.

For EXAMPLE:

A cyclist moving through a busy street does not have a uniform velocity. The velocity of cyclist may change in magnitude, the direction or both. In such a case the cyclist is said to have an accelerated motion, which is positive as it is moving in forward direction or the velocity of the body is increasing with respect to time.

Negative acceleration:

➤ If the velocity of the body is decreasing with respect to time, the acceleration is said to be negative. It is also called deceleration or retardation.

For example:

When we throw the ball UPWARDS i.e, in the upward direction, then the negative acceleration acts on it. As the velocity of an object is negative. Therefore the acceleration is negative.

Unit of acceleration:

In SI system it is expressed in m/s².

N.B - It must be remembered that acceleration is a vector quantity, as it is expressed in magnitude and direction. It is generally represented by letter 'a'.

Give one similarity and one dissimilarity between the GRAPHS:

Ans.

Similarity:

Both the graphs show uniform acceleration that is the body describes equal change in velocity in equal intervals of time.

Dissimilarity:

In the first graph, the object starts from the rest. Therefore the initial velocity is zero, v = 0.
In the second graph, the object does not start from rest, as the object possesses some velocity when it starts that is it possesses some initial velocity, v ≠ 0.

_______________________________