Exercises
1. An athlete comp
letes one round of a circular track of diameter
200 m in 40 s. What will be the distance covered and the
displacement at the end of 2 minutes 20 s?
2. Joseph jogs from one end A to the other end B of a straight
300 m road in 2 minutes 30 seconds and then turns around
and jogs 100 m back to point C in another 1 minute. What are
Joseph's average speeds and velocities in jogging (a) from A to
B and (b) from A to C?
3. Abdul, while driving to school, computes the average speed for
his trip to be 20 km h-l. On his return trip along the same
route, there is less traffic and the average speed is
30 km h-1. What is the average speed for Abdul's trip?
4. Amotorboat starting from rest on a lake accelerates in a straight
line at a constant rate of 3.0 m s-2 for 8.0 s. How far does the
boat travel during this time?
A driver of a car travelling at 52 km h-l applies the brakes and
Answers
Explanation:
1. d=200m
•°• r=100m
t= 2min20sec
•°•t= 140sec
#round completed= 140÷40
= 3.5rounds
AB= 2πr ÷2
a) 2πr(3.5)= 2π×100×3.5
= 44× 50m
= 2200m
b) displacement of AB= 200m
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2. <---------------------------------------->
A-------------300---------C--100--B
a) average speed =300m÷(2×60+30)= 300÷150
=2 m/s
average velocity= 2m/s
b) a. s =400÷210=40÷21 m/s
a. v = 200÷ 210 =20÷21 m/s
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3.
home school
|----------------------------------------------|
A---------------------l----------------------B
t1= l÷20,. t2= l÷30
time average speed of Abdul's trip = 2l÷ t1+t2
= 24m/s
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4. a= 3m/s. ,u= 0m/s ,. t=8sec , s=?
s= ut+ 1a(t) square
2
=. 1÷2× 3×64
= 96m