Question
A motor boat covers a certain distance downstream in a
river in 2 hours. It covers the same distance upstream in 2 hours and 30 minutes. If the speed of water is 3 km/h, then the speed of the boat in still water is:Solution
Let the speed of boat in still water be x km/hr and the distance be y km. Rate downstream = (x + 3) km/hr Rate upstream = (x – 3) km/hr According to the question, y/(x + 3) = 2 --- (i) y/(x – 3) = 5/2 --- (ii) On dividing equation (i) by (ii), (x – 3)/(x + 3) = 2/(5/2) = 4/5 5x – 15 = 4x + 12 x = 15 + 12 = 27 kmph
A simple microscope consists of :
Which of the following instruments is correctly matched with its function?
I) Voltmeter - Measures potential difference
II) Ammeter - Me...
Twinkling of the Stars is due to the phenomenon of
S.I unit of Inductance is
Water gets cooled, when ice is immersed in it. It is because of the phenomenon of
Speed of sound in air is unaffected by change in :
What is the minimum escape velocity required for a rocket to leave Earth's gravitational pull?
‘Therm' is the unit of –
Why a person can jump higher on the Moon’s surface than the Earth?
Which of the following circuit elements is used to 'block' DC in an electronic circuit?