Q1 A girl walks from her home to her friend's house with 4 km/hr.Finding her house locked she returns immediately with x km/hr.If her average speed for the entire trip was 4.8 km/hr then x is(with method plz)
a)5 km/hr
b)4.8 km/hr
c)6 km/hr
d)4.4 km/hr
Q2 A ball is thrown vertically up wards and is caught back by the thrower in 6 seconds.If g= 10m/s²then the speed of his throwing was (with metod plz)
a)10m/s
b)20m/s
C)60m/s
d)30m/s
Answers
Answered by
1
average speed=total distance travelled/total time taken.
let distance of her friends home be a km.
hence Total distance travelled be 2a km.
time taken to reach her friends home=a/4hr
time taken to back to her home=a/ x hr.
4.8= 2a/(a/4 +a/x)
2.4= a/a(1/4+1/x)
2.4= 4x/(x+4)
0.6 = x/(x+4)
2.4=x(1-0.6)
x=6 km/hr
let distance of her friends home be a km.
hence Total distance travelled be 2a km.
time taken to reach her friends home=a/4hr
time taken to back to her home=a/ x hr.
4.8= 2a/(a/4 +a/x)
2.4= a/a(1/4+1/x)
2.4= 4x/(x+4)
0.6 = x/(x+4)
2.4=x(1-0.6)
x=6 km/hr
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