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MrRa [10]
2 years ago
6

As a runner crosses the finish line of a race, she starts decelerating from a velocity of 9 m/s at a rate of 2 m/s^2. Take the r

unner's velocity as she crosses the finish line to be in the positive direction. What is the runner’s displacement, in meters, during the first 5 seconds after crossing the finish line?
What is her velocity, in meters per second, 5 seconds after crossing the finish line?
Physics
1 answer:
Ksivusya [100]2 years ago
4 0

Answer:

- 1 m/s, 20 m

Explanation:

u = 9 m/s, a = - 2 m/s^2, t = 5 sec

Let s be the displacement and v be the velocity after 5 seconds

Use first equation of motion.

v = u + a t

v = 9 - 2 x 5 = 9 - 10 = - 1 m/s

Use second equation of motion

s = u t + 1/2 a t^2

s = 9 x 5 - 1/2 x 2 x 5 x 5

s = 45 - 25 = 20 m

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A stone is thrown vertically upwards with an initial velocity of 20m/sec. Find the maximum height ot reaches and the time taken
MAXImum [283]

Answer:

The height reached is 20m, The time taken to reach 20m is 2 seconds

Explanation:

Observing the equations of motion we can see that the following equation will be most helpful for this question.

v^{2} = u^{2} + 2as

We are given initial velocity, u

We know that the stone will stop at its maximum height, so final velocity, v

Acceleration, a

And we are looking for the displacement (height reached), s

Substitute the values we are given into the equation

0^{2} = 20^{2} + 2(10)s

Rearrange for s

0^{2} -20^{2} =20s

-400=20s

\frac{-400}{20} =s

s = -20 (The negative is just showing direction, it can be ignored for now)

The height reached is 20m

Use a different equation to find the time taken

s = vt - \frac{1}{2} at^{2}

Substitute in the values we have

-20=(0)t - \frac{1}{2} (10)t^{2}

Rearrange for t

-20 =0 -5 t^{2}

\frac{-20}{-5} =t^{2}

4 = t^{2}

t = 2s

The time taken to reach 20m is 2 seconds

4 0
3 years ago
Janelle wants to buy some strings of decorative lights for her home. She is trying to decide between two strings of lights that
inysia [295]
If she has a choice and the wiring details are stated on the packaging,
then Janelle should look for lights that are wired in parallel within the
string, and she should avoid lights that are wired in series within the string. 

If a single light in a parallel string fails, then only that one goes out. 
The rest of the lights in the string continue to shimmer and glimmer.

If a single light in a series string fails, then ALL of the lights in that string
go out, and it's a substantial engineering challenge to determine which light
actually failed.
6 0
3 years ago
Read 2 more answers
If a train is 100 kilometers away, how much sooner would you hear the train coming by listening to the rails (iron) as opposed t
Whitepunk [10]
From tables, the speed of sound at 0°C is approximately
V₁ = 331 m/s (in air)
V₃ = 5130 m/s (in iron)

Distance traveled is
d = 100 km = 10⁵ m

Time required to travel in air is
t₁ = d/V₁ = 10⁵/331 = 302.12 s

Time required to travel in iron is
t₂ = d/V₂ = 10⁵/5130 = 19.49 s

The difference in time is
302.12 - 19.49 = 282.63 s

Answer:  283 s (nearest second)



6 0
2 years ago
A wave travels down the length of a 25-meter rope in 5.0 seconds. The speed of the wave is _____.
Alborosie
Speed
= (distance covered) / (time to cover the distance)

= (25 m) / (5.0 sec) = 5.0 m/s .
4 0
2 years ago
Read 2 more answers
The si unit for acceleration is blank
True [87]

Answer:

meters per second squared

Explanation:

Because acceleration is equal to velocity over time where velocity is meters per second and time is measured in seconds making acceleration ms-2

4 0
2 years ago
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