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3 years ago

A runner achieves a velocity of 11.1 m/s, 9 sec after he begins. What is his

Physics

1 answer:

Elena-2011 [213]3 years ago

7 0

Answer:

1.23 m/s²

Explanation:

Given:

v₀ = 0 m/s

v = 11.1 m/s

t = 9 s

Find: a

Equation:

v = at + v₀

Plug in:

11.1 m/s = a (9 s) + 0 m/s

a = 1.23 m/s²

The runner's acceleration is 1.23 m/s².

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11) A man is on a 1/4 on a bridge. A train is coming the same direction he is going. The man can run across the bridge in the sa

lesya692 [45]

15mph

If the man turns and runs toward point A, he will cover

3/8 of the length of the bridge in the time that it takes

the train to reach A.

If the man runs forward toward point B, what part of the bridge

will he cover before the train reaches A? Well, he will cover

3/8 of the bridge, only heading forward toward B. This will put

him 3/8 + 3/8 = 6/8 = 3/4 of the way across the bridge by the

time the train reaches A.

since we know that the man and the train will meet at B, this

means that in the time it takes the man to run the remaining

1/4 of the bridge, the train will cover the entire length of

the bridge.

If it takes the man the same time to cover 1/4 of the bridge

that it takes the train to cover the whole bridge, then the train

must be going four times as fast as the man. Another way of saying

this is that the man runs at 1/4 the speed of the train.

Since the train's speed is known to be 60 mph, this means that

the man runs at (1/4) 60 = 15 mph.

7 0

2 years ago

The brain mass of a human fetus during a particular trimester can be accurately estimated from the circumference of the head by

Paladinen [302]

Answer:

a. If c = 20 cm, then the mass of the brain is m = 5 g.

b. At c = 20 cm, the brain's mass is increasing at a rate of 15.75 g/cm.

Explanation:

From the equation

$m\left(c\right) = \frac{c^3}{100}-\frac{1500}{c}$

we have

a. for c = 20 cm

$m\left(20\right)=\frac{20^3}{100}-\frac{1500}{20}=5,$

then the mass is m(20) = 5 g.

b. In order to find the rate of change, first we derivate

$\frac{dm}{dc}=\frac{3c^2}{100}+\frac{1500}{c^2}.$

Evaluated at c = 20 cm, we have

$\frac{dm}{dc}|_{c=20}=\frac{3\times 20^2}{100}+\frac{1500}{20^2}=15.75.$

So, at c = 20 cm, the mass of the brain is increasing at a rate of 15.75 g/cm.

3 0

3 years ago

What is the pressure 100m below the surface of the sea , if the density of sea water is 1150kg/m3

Olin [163]

The pressure at 100 meters below the surface of sea water with a density of 1150kg is 145.96 psi.

4 0

2 years ago

A crane exerts a net force of 900 N upward on a 750-kilogram car as the crane starts to lift the car from the deck of a cargo sh

melisa1 [442]

Answer: 1.2m/s^2

Explanation: the force exerted on the car is 900N upwards

The mass of the car is 750kg

According to Newton's third law acceleration is proportional to force

F = ma

900 = 750a

a = 900/750

a = 1.2m/s^2

5 0

3 years ago

When two point charges are a distance d part, the electric force that each one feels from the other has magnitude F. In order to

Contact [7]

Answer:

Because the force is inversely proportional to the square of the distance

Explanation:

The magnitude of the electrostatic force between two charged particles is given by

$F=k\frac{q_1 q_2}{d^2}$

where

k is the Coulomb's constant

q1, q2 are the magnitudes of the two charges

d is the distance between the two charges

We observe that the magnitude of the force is inversely proportional to the square of the distance.

Therefore, when the distance changes to

$d'=\frac{d}{\sqrt{2}}$

The force will double:

$F'=k\frac{q_1 q_2}{(d/\sqrt{2})^2}=2(k\frac{q_1 q_2}{d^2})=2F$

5 0

3 years ago