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diamontehunter1632
26.03.2020 •
Physics
A 2kg object accelerated as a net force acts on it. During the 5 seconds this force acts, the object velocity changes from 3 m/s east to 7m/s west. The initial kinetic energy of the object was 9 joules, and the final kinetic energy was 49 joules
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Ответ:
The force is 4N to the west direction,
Explanation:
Let's define east as +x, and west as -x
The mass of the object is 2 kg.
During 5 seconds, the velocity changes from 3m/s to -7m/s
Now, by the second law of Newton we have that:
F = m*a
This means that the applied force is equal to the mass times the acceleration, and we also know that the integral of the acceleration is equal to the velocity:
a(t) = F/m
v(t) = F/m*t + v0
where v0 is the initial speed, in this case, 3m/s
v(t) = (F/m)*t + v0
at t = 5s, we know that the velocity is -7m/s
-7m/s = (F/2kg)*5s + 3m/s
-10*(2/5)N = F
-4N = F
This means that the force is 4N in the west direction.
The final statement about the kinetic energy does not give any information, because:
k = (1/2)*n*v^2
then
initial energy = (1/2)*2kg*(3m/s)^2 = 9 j
final energy = (1/2)*2kg(-7m/s)^2 = 49 J
Ответ:
Adam
Step-by-step explanation:
You just have to divide feet/second
Adam: 15 feet per second
15/1=15
Noah runs 599 feet in 40 seconds
599/40=14.9
Jake runs 1 mile in 384 seconds
1 mile=5280 feet
5280/384=13.8
liz runs 667 feet in 1 minute
1 minute=60 seconds
667/60=11.1