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3 years ago

Which is not correct when describing the formation of rainbows?

1 answer:

7 0

D- All wave lengths refract at the same angle

Explanation- The amount of refraction increases as the wavelength of light decreases. Shorter wavelengths of light are slowed more and consequently experience more bending than the longer wavelengths.

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A 77.0 kg woman slides down a

statuscvo [17]

Assuming the woman starts at rest, she descends the slide with acceleration a such that

(20.3 m/s)² = 2 a (42.6 m) → a ≈ 4.84 m/s²

which points parallel to the slide.

The only forces acting on her, parallel to the slide, are

• the parallel component of her weight, w (//)

• friction, f, opposing her descent and pointing up the slide

Take the downward sliding direction to be positive. By Newton's second law, the net force in the parallel direction acting on the woman is

∑ F (//) = w (//) - f = ma

where m = 77.0 kg is the woman's mass.

Solve for f :

mg sin(42.3°) - f = ma

f = m (g sin(42.3°) - a)

f = (77.0 kg) ((9.80 m/s²) sin(42.3°) - 4.84 m/s²) ≈ 135 N

Compute the work W done by friction: multiply the magnitude of the friction by the length of the slide.

W = (135 N) (42.6 m) ≈ 5770 N•m = 5770 J

3 0

3 years ago

Immediately after being struck by a hammer, the nail (mass of 50 g) has a velocity of 50 m/s. The total frictional force is 62.5

Marina86 [1]

Answer:

nail will stop after traveling 1000 m

Explanation:

We have given mass m = 50 gram = 0.05 kg

Frictional force which is used to stop the mass F = 62.5 kN

Initial velocity is given u = 50 m/sec

From newton's law force is equal to F = ma, here m is mass and a is acceleration

So $a=\frac{F}{m}=\frac{62.5\times 10^3}{0.05}=1.25\times 10^6m/sec^2$

As finally nail stops so final velocity v = 0 m/sec

From third equation of motion $v^2=u^2+2as$

So $0^2=50^2-2\times 1.25\times 10^6\times s$

s = 1000 m

So nail will stop after traveling 1000 m

8 0

3 years ago

A system of two objects has ΔKtot = 6 J and ΔUint = -5 J. Part A How much work is done by interaction forces? Express your answe

Elina [12.6K]

A) +5 J

B) +1 J

Explanation:

The internal forces (interaction forces) acting on a system do not change the mechanical energy (sum of potential and kinetic energy) of the system.

However, these forces are responsible for converting the energy from one form into another; the work done by these forces is equal to the amount of energy converted from one form into the other.

In this problem, we have:

$\Delta U=-5 J$ is the loss in potential energy of the system

$\Delta K=+6 J$ is the gain in kinetic energy of the system

By looking at these numbers, this means that the internal forces have converted 5 J of energy from potential energy into kinetic energy (while the additional +1 J missing is due to external forces, as explained in part B).

Therefore, the work done by internal forces is

W = +5 J

First of all, we calculate the change in mechanical energy of the system.

The mechanical energy of a system is the sum of its kinetic energy (K) and its potential energy (U):

$E=K+U$

So, the change in mechanical energy is equal to the sum of the changes of kinetic energy and the changes of potential energy:

$\Delta E= \Delta K + \Delta U$

In this problem:

$\Delta K=+6 J$

$\Delta U=-5 J$

So, the change in mechanical energy is:

$\Delta E=+6+(-5)=+1 J$

According to the work-energy theorem, the work done by external forces on a system is equal to the change in mechanical energy of the system: therefore in this case, the work done by external forces is

$W=\Delta E=+1 J$

5 0

4 years ago

The length of a displaced pendulum body which passes its lowest point twice every second

Troyanec [42]

Answer:

0.248 m

Explanation:

The period of a simple pendulum is given by

$T=2\pi \sqrt{\frac{L}{g}}$

where

L is the length of the pendulum

g is the acceleration of gravity

The pendulum in the problem passes its lowest point twice every second: this means: this means that it makes one complete oscillation in one second, so its period is 1 second:

T = 1 s

And using

$g=9.8 m/s^2$

We can rearrange the equation above to find L, the length of the pendulum:

$L=\frac{T^2 g}{4\pi^2}=\frac{1^2(9.8)}{4\pi^2}=0.248 m$

3 0

3 years ago

During the collision of a big truck with a small passenger carGroup of answer choicesthe force from the truck on the car is alwa

lorasvet [3.4K]

Answer:

The force from the truck on the car is always equal to the force from the car on the truck.

Explanation:

According to Newton's third law; action and reaction are equal and opposite. Hence, when the big truck and small passenger car are involved in a collision, we expect that the force from the truck on the car is always equal to the force from the car on the truck. The forces on the car and the truck are equal in magnitude but opposite in direction.

This follows directly from Newton's third law of motion hence the answer above.

3 0

3 years ago