Data:
Time (t) = 5 seconds
Final Velocity (v) = 0 [as the car comes to rest]
<span>Initial velocity (u) = 20 m/s
</span>Acceleration = ? <span>(Negative because it is braking)</span>


Answer:
m = 3.75 [kg]
Explanation:
We must remember that momentum is defined as the product of mass by Velocity, therefore it can be represented by means of the following equation.

where:
P = momentum = 93.75 [kg*m/s]
m = mass [kg]
v = velocity = 25 [m/s]
Now replacing, we can clear the mass:
![P=m*v\\m=P/v\\m=93.75/25\\m=3.75 [kg]](https://tex.z-dn.net/?f=P%3Dm%2Av%5C%5Cm%3DP%2Fv%5C%5Cm%3D93.75%2F25%5C%5Cm%3D3.75%20%5Bkg%5D)
Answer:
n = 1810
A = 25 mm
Explanation:
Given:
Lateral force amplitude, F = 25 N
Frequency, f = 1 Hz
mass of the bridge, m = 2000 kg/m
Span, L = 144 m
Amplitude of the oscillation, A = 75 mm = 0.075 m
time, t = 6T
now,
Amplitude as a function of time is given as:

or amplitude for unforce oscillation

or

or

Now, provided in the question Amplitude of the driven oscillation

the value of the maximum amplitude is obtained
thus,

Now, for n people on the bridge
Fmax = nF
thus,
max amplitude

or
n = 1810
hence, there were 1810 people on the bridge
b)
since the effect of damping in the millenium bridge is 3 times
thus,
b=3b
therefore,

or

or

or
A = 0.025 m = 25 mm