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LenaWriter [7]
3 years ago
9

Highway safety engineers build soft barriers so that cars hitting them will slow down at a safe rate. a person wearing a safety

belt can withstand an acceleration of 300 m/s 2 . how thick should barriers be to safely stop a car that hits the barriers at 92.8 km/h? answer in units of m.
Physics
1 answer:
matrenka [14]3 years ago
5 0
Basically, we want to see the distance in terms of thickness. So, for this rectilinear motion at constant acceleration, the equation to be used is:

x = v₀t + 0.5at²

First, let's determine t using the equation:
a = |v - v₀|/t
300 m/s² = |0 - 92.8 km/h * 1,000 m/1 km * 1 h/3600 s|/t
t = 0.086 seconds

x = (92.8 km/h * 1,000 m/1 km * 1 h/3600 s)(0.086 s) + 0.5(300 m/s²)(0.086 s)²
x = 3.33 meters
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Two rockets are flying in the same direction and are side by side at the instant their retrorockets fire. Rocket A has an initia
lara31 [8.8K]

Answer:

-22.2 m/s²

Explanation:

The equation for position x for a constant acceleration a, time t and initial velocity v₀, initial position x₀:

(1) x=\frac{1}{2}at^2+v_0t+x_0

For rocket A the initial and final position: x = x₀= 0. Using these values in equation 1 gives:

(2) 0=\frac{1}{2}at^2+v_0t

Solving for time t:

-\frac{1}{2}at^2=v_0t

(3) t=-\frac{2v_0}{a}

The times for both rockets must be equal, since they start and end at the same location. Using equation 3 for rocket A and B gives:

(4) \frac{v_{0A}}{a_A}=\frac{v_{0B}}{a_B}

Solving equation 4 for acceleration of rocket B:

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3 0
3 years ago
IMPORTANT 3 QUESTIONS!
Brums [2.3K]

Answer:

7. 20,000,000 mL.

8. 8,000 m.

9. 120,000 secs.

10. 4

Explanation:

7. Determination of the volume in millilitres (mL)

Volume in litre (L) = 20,000 L

Volume in millilitres (mL) =..?

The volume in mL can be obtained as follow:

1 L = 1,000 mL

Therefore,

20,000 L = 20,000 x 1,000 = 20,000,000 mL.

Therefore, 20,000 L is equivalent to 20,000,000 mL.

8. Determination of the distance in metre (m)

Distance in mile = 5 mile

Distance in metre =?

First, we shall convert from mile to kilometre.

This can be done as follow:

1 mile = 1.6 km

Therefore,

5 mile = 5 x 1.6 = 8 km

Finally, we shall convert 8 km to metre (m).

This is illustrated below:

1 km = 1,000 m

Therefore,

8 km = 8 x 1,000 = 8,000 m

Therefore, 5 miles is equivalent to 8,000 m.

9. Determination of the time in seconds.

Time = 400 minutes for 5 days.

First, we shall convert 400 mins to hour.

This is illustrated below:

60 minutes = 1 hour

Therefore,

400 mins = 400/60 = 20/3 hours

The time (hours) is 20/3 hours in 1 day.

Therefore, the time (hours) in 5 days will be = 20/3 x 5 = 100/3 hours.

Next, we shall convert 100/3 hours to minutes.

This is illustrated below:

1 hour = 60 minutes

Therefore,

100/3 hours = 100/3 x 60 = 2000 mins

Finally, we shall convert 2000 mins to seconds.

This is illustrated below:

1 mins = 60 secs

2000 mins = 2000 x 60 = 120,000 secs.

Therefore, the time is 120,000 secs.

10. Determination of the number of significant figures.

To obtain the significant figures of a number, we simply count all the numbers available.

Therefore, the number of significant figures for 9876 is 4.

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