Please give some numericals for velocity and average velocity... Meaningful and for class 9
Answers
Speed: Speed is a scalar quantity which means it has no direction. It denotes how fast an object is moving. If the speed of the particle is high it means the particle is moving fast and if it is low, it means the particle is moving slow.
Velocity: Velocity is a vector quantity which means it has both magnitude and direction. It denotes the rate at which the object is moving or changing position. The direction of the velocity vector is easy to find. Its direction is same as the direction of the moving object. Even if the object is slowing down, and the magnitude of velocity is decreasing, its direction would still be same as the direction in which the object is moving
Average Speed
The average speed of a body in a certain time interval is the distance covered by the body in that time interval divided by time. So if a particle covers a certain distance s in a time t1 to t2, then the average speed of the body is:
vav = st2–t1
In general, average speed formula is:
Average Speed = Total DistanceTotal Time
Now let us look at some of the examples to understand this concept easily
1.) In travelling from Pune to Nagpur , Rahul drove his bike for 2 hours at 60 kmph and 3 hours at 70 kmph.
Sol 1) We know that, Distance = Speed × Time
So, in 2 hours, distance covered = 2 × 60 = 120 km
in the next 3 hours, distance covered = 3 × 70 = 210 km
Total distance covered = 120 + 210 = 330 km
Total time = 2 + 3 = 5 hrs
Avg. Speed = TotaldistancecoveredTimetaken
Avg. Speed = 330/5 = 66 kmph
Average Velocity
The average velocity of a body in a certain time interval is given as the displacement of the body in that time interval divided by time. So if a particle covers a certain displacement AB−→− in a time t1 to t2, then the average velocity of the particle is:
vav−→ =AB−→−t2–t1
In general, the formula is:
Average Velocity= Total DisplacementTotal Time
Understand the concept average velocity through the examples given below.
1) Calculate the average velocity at a particular time interval of a person if he moves 7 m in 4 sec and 18 m in 6 sec along x-axis?
Sol) Initial distance traveled by the person, xi = 7 m,
Final distance traveled, xf = 18 m,
Initial time interval ti = 4 sec,
Final time interval tf = 6 sec,
Average velocity Vav = xi−xftf−ti=18−76−4=112 = 5.5 m/sec.
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Practise This Question
The positions of an elevator are as shown. Could this be uniform motion
pos(floor)581114time(sec)0123
Yes
No
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Practise This Question
Avinash travels half the distance from his home to office at speed of 15 km/hr and rest of the journey at 30 km/hr. Find the average speed of Avinash on his way to office.
10 km/hr
20 km/hr
30 km/hr
15 km/hr
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