A basketball player jumps straight up for a ball. To do this, he lowers his body 0.300 m and then accelerates through this dista
1 answer:
Answer:
a) Vo = 4.24m/s
b) a = 30m/s^2
c) F = 4400N
Explanation:
For part a) we study the movement after he leaves the ground. From that we know:
Where Vf=0 and ΔY=0.9m
Solving for Vo:
For part b) we have to study the movement before he leaves the ground.
Where Vo=0 and ΔY=0.3m
Solving for the acceleration:
For part c) we evaluate forces on the player
The force exerted by the floor on the player is the same as the one exerted by the player on the floor:
Fe - m*g = m*a Fe = m*(g+a) = 4400N
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Answer:
reviewing the opinion of the two students we see that neither is right, since when the kinetic energy increases the potential energy decreases by the same value
Explanation:
For this exercise we must use the law of conservation of energy.
Starting point. Resting electron
Em₀ = U = eV
the potential difference and the electric field are related
V = - E d
Final point. When leaving the electric field
= K = ½ m v²
Em₀ = Em_{f}
e E d = ½ m v²
From this expression we see that when an electron moves from the initial point to the final point, the potential energy must decrease, for the total energy to be constant.
When reviewing the opinion of the two students we see that neither is right, since when the kinetic energy increases the potential energy decreases by the same value
If the elevator was stationary, the scale would read exactly the weight of the person:
However, the elevator is moving with an acceleration a, so the scale reads a new value of the weight, which we call W'. Newton's second law becomes
where a' is actually the total acceleration of the person, so it's the sum of the acceleraion of the elevator and of the gravitational acceleration:
Taking the direction of g (downward) as the positive direction, we can find the value of a:
So, the acceleration of the elevator is
, with same sign of g, so it's directed downward as well.
However, the elevator is moving with an acceleration a, so the scale reads a new value of the weight, which we call W'. Newton's second law becomes
where a' is actually the total acceleration of the person, so it's the sum of the acceleraion of the elevator and of the gravitational acceleration:
Taking the direction of g (downward) as the positive direction, we can find the value of a:
So, the acceleration of the elevator is