The u.s army’s parachuting team, the Golden Knights, are on a routine
1 answer:
The average force is -2600 N
Explanation:
First of all, we need to calculate the acceleration of the man during the collision, which is given by the suvat equation:
where:
v = 0 is his final velocity (he comes to a stop)
u = 4.0 m/s is the initial velocity
a is the acceleration
s = 0.20 m is the distance covered
Solving for a,
The negative sign indicates that it is a deceleration.
Now we can find the average force on the man by using Newton's second law of motion:
where
m = 65 kg is the mass
And substituting,
where the negative sign indicates the force is in the direction opposite to the motion.
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Answer:
d = 0.544 m
Explanation:
To solve this problem we must work in two parts: one when the surface has no friction and the other when the surface has friction
Let's start with the part without rubbing, let's find the speed that the box reaches., For this we use the conservation of mechanical energy in two points: maximum compression and when the box is free (spring without compression)
Initial, maximum compression
Em₀ = Ke = ½ k x²
Final, free box without compressing the spring
= K = ½ m v²
Emo =
½ k x² = ½ m v²
v = √ (k / m) x
Let's reduce the SI units measures
x = 20 cm (1m / 100cm) = 0.20 m
v = √ (100 / 2.5) 0.20
v = 1,265 m / s
Let's work the second part, where there is friction. In this part the work of the friction force is equal to the change of mechanical energy
= ΔEm =
- Em₀
= - fr d
Final point. Stopped box
= 0
Starting point, starting the rough surface
Em₀ = K = ½ m v²
With Newton's second law we find the force of friction
fr = μ N
N-W = 0
N = W = mg
fr = μ mg
-μ m g d = 0 - ½ m v²
d = ½ v² / (μ g)
Let's calculate
d = ½ 1,265² / (0.15 9.8)
d = 0.544 m