the height, y meters, of an object projected directly upwards from the ground can be modelled by y=20t - 5t^2, where t is the time in seconds after it leaves the ground.
a. find the height of the objects 2 seconds after it leaves the ground.
b. when will the object be 15m above the ground?
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Class 11
>>Physics
>>Motion in a Straight Line
>>Speed and Velocity
>>The position of an object moving along x
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The position of an object moving along x-axis is given by x = a + bt
2
, where a = 8.5 m and b = 2.5 m s
−2
and t is measured in seconds. The average velocity of the object between t = 2 s and t = 4 s is
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Correct option is C)
Position is given as x=a+bt
2
=8.5+2.5t
2
Position at t=2 s, x
2
=8.5+2.5(2)
2
=18.5 m
Position at t=4 s, x
1
=8.5+2.5(4)
2
=48.5 m
Displacement S=x
2
−x
1
=48.5−18.5=30 m
Time taken t=4−2=2 s
Average velocity V
avg
=
t
S
=
2
30
=15 m/s
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