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2 years ago

7

How much energy or stopping power is needed to bring a car to a stop from 100 mph?

1 answer:

Fed [463]2 years ago

3 0

I think 100 mph pushing the car the opposite direction

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A train at a constant 79.0 km/h moves east for 27.0 min, then in a direction 50.0° east of due north for 29.0 min, and then west

ivolga24 [154]

Answer:

Magnitude of avg velocity, $|v_{avg}| = 18.9 km/h$

$\theta' = 56.85^{\circ}$

Given:

Constant speed of train, v = 79 km/h

Time taken in East direction, t = 27 min = $\frac{27}{60} h$

Angle, $\theta = 50^{\circ}$

Time taken in $50^{\circ}$ east of due North direction, t' = 29 min = $\frac{29}{60} h$

Time taken in west direction, t'' = 37 min = $\frac{27}{60} h$

Solution:

Now, the displacement, 's' in east direction is given by:

$\vec{s} = vt = 79\times \frac{27}{60} = 35.5\hat{i} km$

Displacement in $50^{\circ}$ east of due North for 29.0 min is given by:

$\vec{s'} = vt'sin50^{\circ}\hat{i} + vt'cos50^{\circ}\hat{j}$

$\vec{s'} = 79(\frac{29}{60})sin50^{\circ}\hat{i} + 79(\frac{29}{60})cos50^{\circ}\hat{j}$

$\vec{s'} = 29.25\hat{i} + 24.54\hat{j} km$

Now, displacement in the west direction for 37 min:

$\vec{s''} = - vt''hat{i} = - 79\frac{37}{60} = - 48.72\hat{i} km$

Now, the overall displacement,

$\vec{s_{net}} = \vec{s} + \vec{s'} + \vec{s''}$

$\vec{s_{net}} = 35.5\hat{i} + 29.25\hat{i} + 24.54\hat{j} - 48.72\hat{i}$

$\vec{s_{net}} = 16.03\hat{i} + 24.54\hat{j} km$

(a) Now, average velocity, $v_{avg}$ is given:

$v_{avg} = \frac{total displacement, \vec{s_{net}}}{total time, t}$

$v_{avg} = \frac{16.03\hat{i} + 24.54\hat{j}}{\frac{27 + 29 + 37}{60}}$

$v_{avg} = 10.34\hat{i} + 15.83\hat{j}) km/h$

Magnitude of avg velocity is given by:

$|v_{avg}| = \sqrt{(10.34)^{2} + (15.83)^{2}} = 18.9 km/h$

(b) angle can be calculated as:

$tan\theta' = \frac{15.83}{10.34}$

$\theta' = tan^{- 1}\frac{15.83}{10.34} = 56.85^{\circ}$

6 0

2 years ago

Do atoms ever touch

Mumz [18]

Answer:

nope never

Explanation:

8 0

2 years ago

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Which statement is the best interpretation of the ray diagram shown below?

madreJ [45]

A) A concave mirror forming a larger, virtual image

Explanation:

The figure is missing; see attachment.

There are two types of mirror:

Concave (converging) mirrors: a concave mirror is a mirror that reflects the light inward
Convex (diverging) mirrors: a convex mirror is a mirror that reflects the light outward

The image formed by a mirror can also be of two types:

Real image: it is formed on the same side of the object, with respect to the mirror
Virtual image: it is formed on the opposite side of the object, with respect to the mirror

In the figure of this problem (see attachment), we see that:

- The mirror reflects the light from the object inward --> so it is a concave mirror

- The image is formed on the other side of the mirror --> it is a virtual image

So the correct option is

A) A concave mirror forming a larger, virtual image

Learn more about mirrors:

brainly.com/question/8737441

#LearnwithBrainly

7 0

2 years ago

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a runner covers the last straight stretch of the race in 4 s. durning that time, he speeds up from 5 m/s to 9m/s what is the run

Sergio039 [100]

Answer:

The runner's acceleration was $1\ m/s^2$

Explanation:

<u>Constant Acceleration Motion</u>

It's a type of motion in which the velocity of an object changes by an equal amount in every equal period of time.

Being a the constant acceleration, vo the initial speed, vf the final speed, and t the time, the following relation applies:

$v_f=v_o+at$

Solving for a:

$\displaystyle a=\frac{v_f-v_o}{t}$

The runner speeds up from vo=5 m/s to vf=9 m/s in t=4 seconds, thus:

$\displaystyle a=\frac{9-5}{4}$

$\displaystyle a=\frac{4}{4}=1$

The runner's acceleration was $1\ m/s^2$

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2 years ago

Hydroelectric power plants can generate huge amounts of electricity. Which of these statements best describes the impact of a hy

Zarrin [17]

The best answer is that it reduces the level of ground water

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2 years ago

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