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steposvetlana [31]
3 years ago
7

The stopping sight distance for a car traveling at 50 mph is 461 ft (including both perception-reaction distance and braking dis

tance). The perception-reaction time is 2.5 sec. If a car traveling at 60 mph is to stop in the same distance with the same deceleration, what is most nearly the required perception-reaction time
Physics
1 answer:
Ivan3 years ago
4 0

Answer:

2.08 s

Explanation:

We are given that

Speed,v=50mph=73.3ft/s

1 mile=5280 feet

1 hour=3600 s

Distance,d=461 ft

t=2.5 s

v'=60 mph=88 ft/s

We have to find the perception reaction time.

Perception reaction distance=d_p=vt=73.3\ti es 2.5=183.25 feet

d_p=d'_p

d'_p=v't

t'=\frac{183.25}{88}=2.08 s

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Given a 45 45 90 prism with index of 1.5, immersed in air. The hypotenuse acts as the reflecting face by TIR. A ray of light ent
Genrish500 [490]

Answer:

83.6°

Explanation:

For the ray to be totally internally reflected, at the boundary, the angle of refraction is 90. Using the law of refraction where

n₁sinθ₁ = n₂sinθ₂ where n₁ = refractive index of prism = 1.5, θ₁ = critical angle in prism, n₂ = refractive index of air = 1 and θ₂ = refractive angle = 90°.

So, substituting these values into the equation,

n₁sinθ₁ = n₂sinθ₂

1.5 × sinθ₁ = 1 × sin90

1.5 × sinθ₁  = 1

sinθ₁ = 1/1.5

sinθ₁ = 0.6667

θ₁  = sin*(0.6667)

θ₁  = 41.8°

So, for total internal reflection, an incidence angle of 41.8° is required. So, a full convergence angle of 2 × 41.8° = 83.6° is required for the whole bundle of rays.

5 0
3 years ago
A person takes a trip, driving with a constant speed of 94.5 km/h except for a 22.0 min rest stop. If the person's average speed
qwelly [4]
From the average speed you can fix an equation:

Average speed = distance / time

You know the average speed = 65.1 kg / h, then

65.1 = distance / total time,

where total time is the time traveling plus 22.0 minutes

Call t the time treavelling and pass 22 minutes to hours:

65.1 = distance / [t + 22/60] ==> distance = [t + 22/60]*65.1

 
From the constant speed, you can fix a second equation

Constant speed = distance / time traveling

94.5 = distance / t ==> distance = 94.5 * t

The distance is the same in both equations, then you have:

[t +22/60] * 65.1 = 94.5 t

Now you can solve for t.

65.1t + 22*65.1/60 = 94.5t

94.5t - 65.1t = 22*65.1/60

29.4t = 23.87

t = 23.87 / 29.4

t  = 0.812 hours

distance = 94.5 km/h * 0.812 h = 76.7 km

Answers: 1) 0.81 hours, 2) 76.7 km


4 0
3 years ago
A 3.0-kg block moves up a 40o incline with constant speed under the action of a 26-N force acting up and parallel to the incline
CaHeK987 [17]

Answer:

it is very hard question for me sorry i cant solve it

3 0
3 years ago
Radar is used to determine distances to various objects by measuring the round-trip time for an echo from the object. (a) How fa
zloy xaker [14]

Answer:

150000000000 m

0.0000005 seconds

33.33 ns

Explanation:

Speed of electromagnetic waves through vacuum = 3\times 10^8\ m/s

Echo time = 1000 seconds

Echo time is the time taken to reach the object and come back to the observer

Distance = Speed×Time

Distance=3\times 10^8\times \frac{1000}{2}=150000000000\ m

Venus is 150000000000 m away from Earth

Time = Distance / Speed

Time=\frac{75}{3\times 10^8}=0.00000025\ seconds

Echo time will be twice the time

Echo\ time=2\times 0.00000025=0.0000005\ seconds

The echo time will be 0.0000005 seconds

Difference in time = Difference in distance / Speed

\Delta t=\frac{\Delta d}{v}\\\Rightarrow \Delta t=\frac{10}{3\times 10^8}\\\Rightarrow \Delta=33.33\ ns

The accuracy by which I will be able to measure the echo time is 33.33 ns

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1 astronomical unit = 149597870700m
Enrico should divide distance in meters with this number.
3 0
3 years ago
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