TNPSC Books
-
TNPSC General English Book - for Group 2 & 2A
Original price was: ₹1,000.00.₹850.00Current price is: ₹850.00.
-
TNPSC பொதுத் தமிழ் Book - for Group 2, 2A, 3, 4 & VAO
Original price was: ₹1,000.00.₹850.00Current price is: ₹850.00.
Group 1 Courses
Group 1 | Postal and Online Test Series | 2022
Original price was: ₹3,200.00.₹2,800.00Current price is: ₹2,800.00. 88
Class Tests
PRIVATE 67
TNPSC Group 1 - Test Series - 2019
Original price was: ₹3,500.00.₹2,800.00Current price is: ₹2,800.00. 542
Group 2 & 2A Courses
Class Tests
PRIVATE 67
TNPSC Group 2 and 2A MAINS - 2022
PRIVATE 344
TNPSC Group 2 and 2A - Test Series - 2019
Original price was: ₹2,400.00.₹1,800.00Current price is: ₹1,800.00. 527
TNPSC Group 2 and 2A - Test Series - 2019 - தமிழ்
Original price was: ₹2,400.00.₹1,800.00Current price is: ₹1,800.00. 175
TNPSC – TIME , SPEED & DISTANCE
Time, Speed and Distance
Speed:
The distance covered per unit time is called speed. Speed is directly proportional to distance and inversely to time
Main units:
Time : Seconds, Minutes, Hours
Distance : meter, kilometre
Speed : km/hr, m/sec
Conversion:
Quicker Method:
==> Average speed: The average speed is given by total distance divided by total time taken.
Average speed = Total Distance / Total Time
= (d1+d2+d3+…dn) / (t1+t2+t3+….tn)
==> The average speed in case of a journey from X to Y at speed of A m/sec and returning back to X at a speed of B m/sec, is [2AB / (A+B)] metre /second
==> Relative Speed
If two trains are moving in opposite directions with a speed of X km/hr respectively, the (X+Y) is their relative speed. In the other case if two trains are moving in the same direction with a speed of X km/hr and Y km/hr respectively, then (X-Y) is their relative speed.
For the first case the time taken by the trains in passing each other
= (L1+L2) / (X+Y) hours,
where L1 and L2 are lengths of the trains.
For the second case the time taken by the trains in passing each other
= (L1+L2) / (X-Y) hours,
Where L1 and L2 are lengths of the trains.
==> The time taken by a train X meters long to pass a signal post is the time taken for the train to cover X meters.
==> The time taken by a x meters long train in passing any object which is y meters long is the time taken for the train to cover the distance x+y.
BOAT & STREAM
When we move upstream, our speed gets deducted from the speed of the train. Similarly, when we move downstream our speed gets added to the speed of the stream.
Let the speed of a boat in still water be A km/hr and the speed of the stream (or current) be B km/hr, then
==> Speed of boat with the stream i.e speed downstream = (A+B) km/hr
==> Speed of boat against the stream i.e speed upstream = (A-B) km/hr
==> Boat’s speed in still water = (speed downstream (D) + Speed upstream (U)) / 2
==> Speed of current = (speed downstream (D) – Speed upstream (U)) / 2
Quicker method:
Example 1:
A boat travels equal distances upstream and downstream. The upstream speed of boat was 10 km/hr, whereas the downstream speed is 20 km/hr. What is the speed of the boat in still water?
Soln.
Upstream speed = 10 km/hr
Downstream speed = 20 km/hr
As per formula, Boat’s speed in still water = (speed downstream (D) + Speed upstream (U)) / 2
Therefore, Boat’s speed in still water = (10+20) / 2 = 15 km/hr
Example 2:
A boat travels equal distance upstream and downstream. The upstream speed of boat 10 km/hr, whereas the downstream speed is 20 km/hr. What is the speed of the current?
Soln.
Upstream speed = 10 km/hr
Downstream speed = 20 km/hr
As per formula, Speed of Current = (speed downstream (D) – Speed upstream (U)) / 2
Therefore, Speed of Current = (20-10) / 2 = 10/2 = 5 km/hr.