Harvard Collection of Historical Scientific Instruments Harvard Museums Time Trails Harvard CHSI
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Total Gadha_s Complete Book of Time Speed and Distance_5
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SCIENCE
Problems on Superposition Time and Space
time and motion
HANDOUT FOR TIME AND WORK
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1 A peon walks from P to Q at the rate of 5 kmph. After transacting some business which occupies him an hour, returns to P by the tramway at the rate of 7 kmph. He then finds that he has been absent for 2 hours 2 minutes. !ind the distance distance from P to Q. "# "# 2.$ 2.$ km km "2# "2# %.5 %.5 km km "%# "%# &.2 &.2 km km " " 2. 2. km km
'(5 ) ) '(7 * 2"2(+# *- ' * %.5 km. 2 ha/e to be at a certain place at a certain time and find that shall be 5 minutes too late, if walk at & kmph0 and minutes too early if walk at + kmph. How far ha/e to walk1 "# & km
A train tra/elling at 55 kmph lea/es 4umbai at + am and another train starts from 4umbai at am in the same direction at the speed of +5 kmph. How many km from 4umbai will the two trains be together1 "# "# $& $& km "2# "2# 2& 2& m "%# "%# 2& 2& km " 72.5 72.5 km 6he first train has a start start of 55 % km and the second train train gains "+5 355# or km per hour. hour. will gain 55 % km in +5( * +.5 hrs. ∴ 6he reuired distance from 4umbai * +5 8 +.5 km * 72.5 km.
6he second train
& 6he distance of the sun from the earth is one hundred forty three million four hundred thousand km and light tra/els from the former to the latter in se/en minutes and fifty eight seconds. !ind the speed of l ight per second. "# "# % 5 km (sec "2# "2# % 5 m (sec "%# "%# % 5 + m (sec " " %.7 %.7 5 km (sec 9peed of light * &%& km ( " 7 + ) 5$# 9ec * % km(sec. 5 6he wheel of an engine %(7 m in circumference makes se/en re/olutions in & seconds. !ind the speed of the train in kmph. "# "# $ km(s km(s "2# 27 km(hr km(hr "%# "%# 5& m(h m(hrr " " 2 m(s
'istance co/ered by the wheel in 7 re/olutions "%(7# 7 * % metres in & sec. 9peed * %(& m(sec * 7.5 m(sec *- 7.5 $(5 km(hr * 27 km(hr.
6 9ound tra/els at %% m(s. How many kilometers is a thunder:cloud located when the sound follows the flash after seconds1 "# %% km "2# %.% km "%# %.% m " %% m %% metres * %% m * %.% km. 7 6wo trains tra/el in the same direction at 5+ kmph and 2 kmph and the faster train passes a man in the slower train in + seconds. !ind the length of the faster train. "# 2$ m "2# %2 m "%# 2 m " $ m n one hour faster train gains * 5+ 3 2 * 27 km. n one second it gains 27 5($ * 7; m. and ? 6hen '(? ) '(> * +.5 and 2'(? * +.5 3 2 "(+# * %(% *- '(? * %(+ *- '(> * %(%. * 2+(% * $ hrs. & min
9 6wo ships left a port at the same time. @ne started sailing towards the north and the other towards the west. 6he speed of one was + kmph faster than the other. 6wo hours after their start, they were + km apart. !ind the speed of the slower ship. "# 2 kmph "2# 5 kmph "%# $ kmph " 2& kmph
10
6wo boys begin together to write out a book containing $7 lines. 6he first boy starts with the first line, writing at the rate of 2 lines an hour0 and the second boy starts with the last line, then writes line $+ and so on, backwards at the rate of 5 lines an hour. At what line will they meet1 "# %5th line "2# &+7th line "%# %25th line " %7+th line elati/e speed * 2 ) 5 * %5 lines(hour. 6ime reuired to meet * $7(%5 * 2.%% hours. n 2.%% hours, the first writes 2.%% 2 * &++.$ lines. *- 6hey meet at &+7th line. 11 A, B and C can walk at the rate of %, &, 5 kmph. 6hey start from 4umbai at , 2, % pm respecti/ely. Dhen B catches A, B sends him back with a message to C. At what time will C get the message1
"# &E&5 pm "2# 5E5 pm "%# 5 pm " &E5 pm B starts one hour after A. n:one hour A co/ers % km. B will take %("& 3 %# * % hours to catch A. *- B catches A at 5 oFclock.
"# &$ km "2# 5+ km "%# %$ km " km =et the distance be '. *- '( 3 '( * %2(+ *- ' * &$ km. Ans.(1) 16 A motor car completes a Gourney in hours, the first half at 2 kmph and the rest at 2& kmph. !ind the distance. "# 2%2 km "2# 25 km "%# 22& km " 2&$ km
=et the distance be '. *- ""'(2# ( 2# ) ""'(2# ( 2 * *- ' * 22& km. Ans.(3)
17 A man walks from A to B and back in a certain time at the rate of %.5 kmph. But if he had walked from A to B at the rate of % kmph and back from B to A at the rate of & kmph, he would ha/e taken 5 minutes longer. !ind the distance between A and B. "# %.5 km "2# +.5 km "%# + km " 7 km =et the distance be ' *- 2'(%.5 3 5(+ * '(% ) '(& *- ' * 7 km. Ans.(4) 18 A man rode out a certain distance by train at the speed of 25 kmph and walked back at the speed of & kmph, 6he whole Gourney occupied 5 hours &$ minutes. Dhat distance did he ride1 "# 25 km "2# $ km "%# + km " 2 km =et the distance be '. '(25 ) '(& * 5"&$(+# *- ' * 2 km. Ans.(4)