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QveST [7]
3 years ago
14

A sprinter moving at 10 m/s slows down at a rate of 1.4 m/s2. how fast is the runner moving after 4 seconds?

Physics
2 answers:
Tema [17]3 years ago
6 0

Answer:

vf= 4.4 m/s

Explanation:

Kinematics

Because the sprinter moves with uniformly accelerated movement we apply the following formula:

vf= v₀+at Formula (1)

Where:  

t : time in seconds (s)

v₀: initial speed in m/s  

vf: final speed in m/s  

a: acceleration in m/s²

Data

t = 4 s

v₀ = 10 m/s

a = -1.4 m/s²

Problem development

We replace data in the formula (1) to calculate the speed of the sprinter in 4 seconds :

vf = 10-1.4(4)

vf= 4.4 m/s

AURORKA [14]3 years ago
3 0
V=u+at
v=10+(-1.4 (4))
=10-5.6
=4.4m/s
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Before the firecracker blows a coconut does not move, so left side is equal to 0:
0 = m_{1} v_{1f} + m_{2} v_{2f} + m_{3} v_{3f}

We know that m1=m2=m and m3=2m. Also we are asked to find v3f so we can rewrite formula:
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We must take in consideration that two parts with same mass do not move in same direction. The center of mass of these two parts moves between them at angle of 45° with respect to both south and west. The speed of a center of mass is:
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v_{3f} = - \frac{m*33.9+m*33.9 }{ 2m } \\  \\ v_{3f} = - \frac{2m*33.9 }{ 2m }  \\  \\ v_{3f} = - 33.9m/s

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