a 100 kg gymnast comes to a stop after tumbling. her feet do -5000J of net work to stop her. Use the work-kinetic energy theorem
2 answers:
Answer:
10 m/s
Explanation:
The work-kinetic energy theorem states that the net work done on an object is equal to the change in the kinetic energy of the object.
In formula:
(1)
where
W is the work done
Ki is the initial kinetic energy
Kf is the final kinetic energy
In this problem, we have:
the net work done on the gymnast
is the mass of the gymnast
is the final velocity of the gymnast, so her final kinetic energy is also zero:
Therefore, we can rewrite eq.(1) as
where is the initial velocity of the girl. By substituting the numbers and re-arranging the equation, we find:
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Answer:
maximumforce is F = mg
Explanation:
For this case we must use Newton's second law,
Σ F = m a
bold indicate vectors, so we will write it in its components x and y
X axis
Fₓ = maₓ
Axis y
Fy - W = m a
Now let's examine our case, with indicate that the bird is level, the force of the wings can have a measured angle with respect to the x axis, where the vertical component is responsible for the lift, let's use trigonometry to find the components
Cos θ = Fₓ / F
Fₓ = F cos θ
sin θ = Fy / F
Fy = F sin θ
Let's replace and calculate
F sin θ -w = m a
As the bird indicates that leveling at the same height, so the vertical acceleration is zero (ay = 0)
F sin θ = w = mg
The maximum value of this equation occurs when the sin=1, in this case
F = mg