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3 years ago

Examine the scenario.

Physics

1 answer:

vovangra [49]3 years ago

7 0

Answer:

acceleration 8 km/h/s south

Explanation:

First of all, let's remind that a vector quantity is a quantity which has both a magnitude and a direction.

Based on this definition, we can already rule out the following two choices:

distance: 40 km

speed: 40 km/h

Since they only have magnitude, they are not vectors.

Then, the following option:

velocity: 5 km/h north

is wrong, because the car is moving south, not north.

So, the correct choice is

acceleration 8 km/h/s south

In fact, the acceleration can be calculated as

$a=\frac{v-u}{t}$

where

v = 40 km/h is the final velocity

u = 0 is the initial velocity

t = 5 s is the time

Substituting,

$a=\frac{40 km/h-0}{5 s}=8 km/h/s$

And since the sign is positive, the direction is the same as the velocity (south).

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A motorcycle of mass 100 kilograms slowly rolls off the edge of a cliff and falls for three seconds before reaching the bottom o

Jet001 [13]

Answer:

C) 3,000 kg m/s

Explanation:

We can consider the horizontal velocity of the motorcycle to be zero, since it rolls off the edge of the cliff very slowly. So, we only need to find the vertical velocity at the time of the impact with the ground.

The vertical velocity of the motorcycle at time t is given by (free-fall motion):

$v(t)=v_0 -gt$

where

$v_0=0$ is the initial vertical velocity (zero, since the motorcycle is not moving)

g = 9.8 m/s^2 is the acceleration due to gravity

t is the time

Since the motorcycle hits the ground after t = 3 seconds, we have

$v(3 s)=0-(9.8 m/s^2)(3 s)=-29.4 m/s$

And since we know its mass, m=100 kg, we can find its momentum:

$p=mv=(100 kg)(-29.4 m/s)=-2940 kg m/s \cdot -3000 kg m/s$

and the negative sign simply means downward direction.

8 0

3 years ago

A mass weighing 14 pounds stretches a spring 2 feet. The mass is attached to a dashpot device that offers a damping force numeri

Elodia [21]

Answer:

The motion is over-damped when λ^2 - w^2 > 0 or when $b^{2}$ > 0.86

The motion is critically when λ^2 - w^2 = 0 or when $b^{2}$ = 0.86

The motion is under-damped when λ^2 - w^2 < 0 or when $b^{2}$ < 0.86

Explanation:

Using the newton second law

k is the spring constante

b positive damping constant

m mass attached

$m\frac{d^{2} x}{dt^{2}} = - kx - b\frac{dx}{dt}$

x(t) is the displacement from the equilibrium position

$\frac{d^{2} x}{dt^{2}} +\frac{b}{m}\frac{dx}{dt} + \frac{k}{m}x = 0$

Converting units of weights in units of mass (equation of motion)

$m = \frac{W}{g} = \frac{14}{32} = 0.43 slug$

From hook's law we can calculate the spring constant k

$k = \frac{W}{s} = \frac{14}{2} = 7 lb/ft$

If we put m and k into the DE, we get

$\frac{d^{2} x}{dt^{2}} +\frac{b}{0.43}\frac{dx}{dt} + 16.28x = 0$

Denoting the constants

2λ = $\frac{b}{m}$ = $\frac{b}{0.43}$

λ = b/0.215

$w^{2} = \frac{k}{m} = 16.28$

λ^2 - w^2 = $\frac{b^{2} }{0.046} - 16.28$

This way,

The motion is over-damped when λ^2 - w^2 > 0 or when $b^{2}$ > 0.86

The motion is critically when λ^2 - w^2 = 0 or when $b^{2}$ = 0.86

The motion is under-damped when λ^2 - w^2 < 0 or when $b^{2}$ < 0.86

3 0

3 years ago

A proton traveling due north enters a region that contains both a magnetic field and an electric field. The electric field lines

Bess [88]

Answer:

upward

Explanation:

In the electromagnetic system of force if the direction of motion of proton does not changes it means that the electric and magnetic forces are such a ways that they are cancelling each other's effect.

Since, electric field lines will exert a force on the proton to the west, hence, the magnetic force must force it to the east. It is well known that magnetic force acts perpendicular to the direction of magnetic field. magnetic field should point upward direction.

3 0

3 years ago

A hot air balloon must be designed to support a basket, cords, and one person for a total payload weight of 1300 N plus the addi

RSB [31]

Answer:

r = 4.44 m

Explanation:

For this exercise we use the Archimedes principle, which states that the buoyant force is equal to the weight of the dislodged fluid

B = ρ g V

Now let's use Newton's equilibrium relationship

B - W = 0

B = W

The weight of the system is the weight of the man and his accessories (W₁) plus the material weight of the ball (W)

σ = W / A

W = σ A

The area of a sphere is

A = 4π r²

W = W₁ + σ 4π r²

The volume of a sphere is

V = 4/3 π r³

Let's replace

ρ g 4/3 π r³ = W₁ + σ 4π r²

If we use the ideal gas equation

P V = n RT

P = ρ RT

ρ = P / RT

P / RT g 4/3 π r³ - σ 4 π r² = W₁

r² 4π (P/3RT r - σ) = W₁

Let's replace the values

r² 4π (1.01 10⁵ / (3 8.314 (70 + 273)) r - 0.060) = 13000

r² (11.81 r -0.060) = 13000 / 4pi

r² (11.81 r - 0.060) = 1034.51

As the independent term is very small we can despise it, to find the solution

r = 4.44 m

3 0

4 years ago

Which simple experiment could be conducted to show an example of how lightning is created? A) Rub a balloon so it picks up extra

alexandr1967 [171]

I think the answer is d

7 0

3 years ago