Question
plz tell me different between vector and scalar and what,s resultant vector plz explain.
Answer
Scalar Quantities:
Most of the physical quantities encountered in physics are either scalar or vector
quantities. A scalar quantity is defined as a quantity that has magnitude only. Typical
examples of scalar quantities are time, speed, temperature, and volume. A scalar quantity
or parameter has no directional component, only magnitude. For example, the units for
time (minutes, days, hours, etc.) represent an amount of time only and tell nothing of
direction. Additional examples of scalar quantities are density, mass, and energy.
Vector Quantities
A vector quantity is defined as a quantity that has both magnitude and direction. To work
with vector quantities, one must know the method for representing these quantities.
Examples of Vector Quantities
Displacement, velocity, acceleration, and force are examples of vector quantities. Momentum and
magnetic field strength are also good examples of vector quantities, although somewhat more difficult to
understand. In each of these examples, the main ingredients of magnitude and direction are present.
Resultant Vector
A resultant is a single vector which represents the combined effect of two or more other
vectors (called components). The components can be determined either graphically or by
using trigonometry.
Question
sir plz define average velocity and average accelration.
First of all you should clear about vector and scalar quantities. Keep in mind speed is a
scalar quantity and velocity is a vector quantity. In order to understand the average
velocity first tries to understand the average speed. After it I hope you will clearly
understand average velocity.
Average speed and average velocity are not the same quantity, and they are calculated
differently. This is not just because velocity is a vector and speed is not; it has to do with
distance and displacement. On this page we'll show you how to calculate both average
speed and average velocity, and explain why they're different.
Average Speed
Average
speed
is
not
a
vector
quantity.
It
has
no
direction.
The simplest way to find average speed is to divide the total distance travelled by the
total time taken.
Have a look at the path followed by the child shown below.
She has travelled a total distance of 12 metres, and has stopped 3 metres from where she
began.
Let's suppose she covered each leg of her journey in one second. This means that the
total time for her trip was 6 seconds.
Her average speed is the total distance she covered, divided by the total time taken.
Since she covered a total distance of 12 metres in 6 seconds, her average speed for the
trip is 2 m/s.
Which direction she went, or where she ended up, is unimportant, as long as we know the
sum of all the distances she travelled, and how long it took.
Average Velocity
Average velocity is based on where she ended her trip; specifically, how far she is from
her starting point. This distance from the starting point is called displacement, and it's a
vector quantity.
In the picture above, you can see that the child's displacement is 3 metres right from
where she started. (Notice that displacement comes with a direction). Her average
velocity is based on this quantity, not what she did to get there.
Since her displacement from where she started was 3 metres to the right, and this trip
took a total of 6 seconds, her average velocity was 3 m divided by 6 s, or 0.5 m/s right.
Again, notice that the average velocity does not depend on where you went before you
got to where you ended up. All that matters is how far you ended up from where you
started (displacement), and how long it took. Here's another example to make that clearer.
Path 1:
The average speed was 30 m divided by 6 seconds, or 5 m/s.
The average velocity was 12 metres divided by 6 seconds, or 2 m/s (in a direction that's
approximately 110° from vertical).
Path 2:
The average speed was 18 m divided by 6 seconds, or 3 m/s.
The average velocity was 12 metres divided by 6 seconds, or 2 m/s (in a direction that's
approximately 110° from vertical).
Both trips have the same average velocity despite very different paths, because they
ended at the same spot (displacement) and took the same amount of time to get there.
Average Acceleration
Average acceleration is the rate at which velocity changes. Average acceleration is the
change in velocity divided by an elapsed time. For instance, if the velocity of a marble
increases from 0 to 60 cm/s in 3 seconds, its average acceleration would be 20 cm/s/s.
This means that the marble’s velocity will increase by 20 cm/s every second. See the
table below:
Time (Seconds) Velocity (cm/s)
0
0
1
20
2
40
2
60
4
80
Here is the formula we will use:
Average Acceleration =  Velocity
 Time
 = “change in” or “difference of”