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Naddika [18.5K]
3 years ago
15

A red train traveling at 72 km/hr and a green train traveling at 144 km/hr are headed toward one another along a straight level

track. When they are 950 meters apart, each enginneer sees the other's train and applies the brakes. The brakes decelerate each train at the rate of 2.0 m/s^2. Is there a colllision? If so, what is the speed of each train at impact? If not, what is the separtion between the trains when they stop?
Physics
1 answer:
Temka [501]3 years ago
5 0
First, convert all the km/hr into m/s

You will get that
initial speed = 20 m/s
Initial speed of Green train = 40 m/s
Initial separation = 950 m
Velocity of approach =  20 - -40 = 60 m/s
relative acceleration = -4 m/s^2

v = u + at
0 = 60 - 4t

t = 15s

s = ut + 1/2  *at * t

s = 60 * 15  - 1/2 *4 * 225
s = 900 - 450

Separation when they stop  = 450 m

hope this helps

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Answer:

r=2.4m

Explanation:

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Fc=\frac{mv^{2} }{r}

we  need the radious so we have to isolate "r" and we get

r=\frac{mv^{2} }{Fc}

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4 0
3 years ago
The platform height for Olympic divers is 10 m. A 60 kg diver steps off the platform to begin his dive.
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Answer:

a) Ep = 5886[J]; b) v = 14[m/s]; c)   W = 5886[J]; d) F = 1763.4[N]

Explanation:

a)

The potential energy can be found using the following expression, we will take the ground level as the reference point where the potential energy is equal to zero.

E_{p} =m*g*h\\where:\\m = mass = 60[kg]\\g = gravity = 9.81[m/s^2]\\h = elevation = 10 [m]\\E_{p}=60*9.81*10\\E_{p}=5886[J]

b)

Since energy is conserved, that is, potential energy is transformed into kinetic energy, the moment the harpsichord touches water, all potential energy is transformed into kinetic energy.

E_{p} = E_{k} \\5886 =0.5*m*v^{2} \\v = \sqrt{\frac{5886}{0.5*60} }\\v = 14[m/s]

c)

The work is equal to

W = 5886 [J]

d)

We need to use the following equation and find the deceleration of the diver at the moment when he stops his velocity is zero.

v_{f} ^{2}= v_{o} ^{2}-2*a*d\\where:\\d = 2.5[m]\\v_{f}=0\\v_{o} =14[m/s]\\Therefore\\a = \frac{14^{2} }{2*2.5} \\a = 39.2[m/s^2]

By performing a sum of forces equal to the product of mass by acceleration (newton's second law), we can find the force that acts to reduce the speed of the diver to zero.

m*g - F = m*a

F = m*a - m*g

F = (60*39.2) - (60*9.81)

F = 1763.4 [N]

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t = 2.13 s

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Answer:

c

Explanation:

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