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4 years ago

Is the speed of the object is zero when it's at rest ?

Physics

1 answer:

NARA [144]4 years ago

4 0

Yes! Although the object has potential energy, the object is not moving and therefore has no speed. :)

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A fugitive tries to hop a freight train traveling at a constant speed Of 4.5 m/s. Just as a empty box car passes him, the fugiti

Dominik [7]

We use the kinematics equation:
Vf = Vi + a*t
8 = 0 + 3.6 * t
t=2.222s to reach 8.0 m/s

At that time the train has moved
4.5 m/s * 2.222s = 9.999 m

He travelled (another kinematics equation)
Vf^2 = Vi^2 + (2*a*d)
(8.0)^2 = (0)^2 + (2 * 3.6 * d)
d=8.888 m

The train is 9.999m, the fugitive is 8.888m,
He still needs to travel
9.999-8.888= 1.111m

He needs to cover the rest of the distance in a smaller amount of time, however hes at his maximum velocity, so...
8m/s(man) - 4.5m/s(train) = 3.5 m/s more

(1.111m) / (3.5m/s) = .317seconds more to reach the train

So if it takes 2.222 seconds to approach the train at 8.888m, it should take
2.222 + .317 =2.529 seconds to reach the train completely

Last but not least is to figure out the total distance traveled in that time frame:

(Trains velocity) * (total time)

(4.5m/s)*(2.529s)=11.3805m

8 0

3 years ago

A device called an insolation meter is used to measure the intensity of sunlight. It has an area of 100 cm2 and registers 6.50 W

labwork [276]

Answer:

Explanation:

Intensity of the sunlight is expressed as I = Power/cross sectional area. It is measured in W/m²

Given parameters

Power rating = 6.50Watts

Cross sectional area = 100cm²

Before we calculate the intensity, we need to convert the area to m² first.

100cm² = 10cm * 10cm

SInce 100cm = 1m

10cm = (10/100)m

10cm = 0.1m

100cm² = 0.1m * 0.1m = 0.01m²

Area (in m²) = 0.01m²

Required

Intensity of the sunlight I

I = P/A

I = 6.5/0.01

I = 650W/m²

Hence, the intensity of the sunlight in W/m² is 650W/m²

4 0

3 years ago

What clues should you look for to determine if an authors purpose is to make you think deeply

8090 [49]

If the context is difficult to understand they want you to think hard to get what their trying to say and make you feel a certain way.

7 0

3 years ago

A specimen of aluminum having a rectangular cross section 9.5 mm × 12.9 mm (0.3740 in. × 0.5079 in.) is pulled in tension with 3

ryzh [129]

Answer:

The resultant strain in the aluminum specimen is $4.14 \times {10^{ - 3}}$

Explanation:

Given that,

Dimension of specimen of aluminium, 9.5 mm × 12.9 mm

Area of cross section of aluminium specimen,

$A=9.5\times 12.9=123.84\times 10^{-6}\ mm^2A=122.55\times 10^{-6}\ m^2$

Tension acting on object, T = 35000 N

The elastic modulus for aluminum is, $E=69\ GPa=69\times 10^9\ Pa$

The stress acting on material is proportional to the strain. Its formula is given by :

$\epsilon=\dfrac{\sigma}{E}$

$\sigma$ is the stress

$\epsilon=\dfrac{F}{EA}\\\epsilon=\dfrac{35000}{69\times 10^9\times 122.5\times 10^{-6}}\\\epsilon=4.14\times 10^{-3}$

Thus, The resultant strain in the aluminum specimen is $4.14 \times {10^{ - 3}}$

5 0

4 years ago

Read 2 more answers

Can you please help me with this physics question

erastova [34]

Answer:

See the answers below

Explanation:

We can solve both problems using vector sum.

Let's assume the forces that help the diver dive as positive downward, and the forces that oppose upward, as negative

$F_{resultant}=100+30-85+900\\F_{resultant}=845[N]$

The drag force is horizontal d this way in the horizontal direction we will only have the drag force that produces the water stream.

$F_{drag}=50[N]$

Let's assume the forces that propel the rocket upwards as positive and forces like the weight of the rocket and other elements as negative forces.

$F_{resultant}=960+7080-7700\\F_{resultant}=340 [kN]$

6 0

3 years ago