A rock falls from rest off a high cliff. How much time does it take for the rock to reach a speed of 40 m/s? [ignore air resista
1 answer:
You might be interested in
Answer:
d = 0.38 m
Explanation:
As we know that the person due to the airbag action, comes to a complete stop, in 36 msec or less, and during this time, is decelerated at a constant rate of 60 g, we can find the initial velocity (when airbag starts to work), as follows:
vf = v₀ -a*t
If vf = 0, we can solve for v₀:
v₀ = a*t = 60*9.8 m/s²*36*10⁻³s = 21.2 m/s
With the values of v₀, a and t, we can find Δx, applying any kinematic equation that relates all of some of these parameters with the displacement.
Just for simplicity, we can use the following equation:
where vf=0, v₀ =21.2 m/s and a= -588 m/s².
Solving for d:
⇒ d = 0.38 m