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4 years ago

Work: If the force on an object is in the negative direction, the work it does on the object must be

Physics

1 answer:

dimulka [17.4K]4 years ago

5 0

Answer:

The work must be negative or positive depending on direction of motion of the object

Explanation:

This is because

W= force x distance

And = F x S cosစ

And this is positive when

Theta is less than π/2 and negative when theta is less than or equal to π/2

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Convert 45 hours into days

xenn [34]

1.875 is your answer

3 0

3 years ago

Although the evidence is weak, there has been concern in recent years over possible health effects from the magnetic fields gene

Natasha2012 [34]

Answer:

A. $B = 6.36 * 10^{-10} T$

B. P ≈ 0

Explanation:

In order to calculate the magnetic field strength we have to use the magnetic field strength of a straight wire.

$B = \frac{mi* I}{2\pi *d}$ (eq. I)

B = magnetic field strength at distance d

I = current (A)

mi = represented by the greek letter μ, represents the permeability of the free space, which is: 4 × π 10^(-7) T m/A

d = distance from the wire

By replacing the values in eq I, we have the following:

$B = \frac{4\pi 10^{-7} T m A^{-1} 200 A}{2\pi *20 m}\\\\B = 6.36 * 10^{-10} T\\$ (eq II)

The earth magnetic field in the surface variates from 25 to 65 microteslas. Thus:

P = Percentage from the wires/percentage of the earth

$P = \frac{6.36 * 10^{-10}T}{65* 10^{-3} T}\\$ ∵ $B$ ∴

P ≈ 0

5 0

4 years ago

Train cars are coupled together by being bumped into one another. Suppose two loaded train cars are moving toward one another, t

NemiM [27]

Answer:

their final velocity is 0.091 m/s

Explanation:

Given;

mass of the first train, m₁ = 138,000 kg

mass of the second train, m₂ = 123,000 kg

initial velocity of the first train, u₁ = 0.288 m/s

initial velocity of the seocnd train, u₂ = -0.131 m/s (opposite direction to the first)

Let their common final velocity after been coupled = v

Apply the principle of conservation of linear momentum;

m₁u₁ + m₂u₂ = v(m₁ + m₂)

(138,000 x 0.288) + (-0.131 x 123,000) = v(138,000 + 123,000)

39,744 - 16,113 = v(261,000)

23,631 = v(261,000)

v = 23,631 / 261,000

v = 0.091 m/s

Therefore, their final velocity is 0.091 m/s

5 0

3 years ago

In experimental design: What are<br> the two groups?

sp2606 [1]

Answer:

The correct answer is : a special type of experimental design where subject divides in two groups according their treatment setting.

Explanation:

A two group is a experimental design two groups are the two different groups of subjects divided by the researcher for comparing the data and result to establish relation in variables.

In normal case, one of the two groups one is a group of subjects who get treatment known as experiment or treatment group while other group is known as control group without treatment.

Thus, the correct answer is : a special type of experimental design where subject divides in two groups according their treatment setting.

7 0

3 years ago

A ball rolls horizontally off a table and a height of 1.4 m with a speed of 4 m/s. How long does it take the ball to reach the g

Hitman42 [59]

For vertical motion, use the following kinematics equation:

H(t) = X + Vt + 0.5At²

H(t) is the height of the ball at any point in time t for t ≥ 0s

X is the initial height

V is the initial vertical velocity

A is the constant vertical acceleration

Given values:

X = 1.4m

V = 0m/s (starting from free fall)

A = -9.81m/s² (downward acceleration due to gravity near the earth's surface)

Plug in these values to get H(t):

H(t) = 1.4 + 0t - 4.905t²

H(t) = 1.4 - 4.905t²

We want to calculate when the ball hits the ground, i.e. find a time t when H(t) = 0m, so let us substitute H(t) = 0 into the equation and solve for t:

1.4 - 4.905t² = 0

4.905t² = 1.4

t² = 0.2854

t = ±0.5342s

Reject t = -0.5342s because this doesn't make sense within the context of the problem (we only let t ≥ 0s for the ball's motion H(t))

t = 0.53s

8 0

4 years ago

Read 2 more answers