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Kryger [21]
4 years ago
11

Your average speed on the first half of a car trip is 69.0 km/h. How fast do you have to drive on the second half of the trip to

achieve an average speed of 82.0 km/h for the whole trip
Physics
1 answer:
vova2212 [387]4 years ago
3 0

Answer:

13 km/h

Explanation:

Average speed = distance/time

Let the total distance and total time taken for the whole trip be d km and t hours respectively

Average speed for the whole trip = 82 km/h

d = 82t

The distance covered in the first half = d1/2

Time taken = t/2

Average speed = 69 km/h

69 = d1/2 ÷ t/2

d1 = 69t

The distance covered in the second half = d2/2

Time taken = t/2

Let the average sly for the see half be A

A = d2/2 ÷ t/2

d2 = At

d = d1 + d2

82t = 69t + At

At = 82t - 69t

At = 13t

A = 13t/t = 13 km/h

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A record turntable is rotating at 33 rev/min. A watermelon seed is on the turntable 4.0 cm from the axis of rotation. (a) Calcul
Annette [7]

Answer:

a) a = 0.477 m/s^2

b) u = 0.04862

Explanation:

Given:-

- The rotational speed of the turntable N = 33 rev/min

- The watermelon seed is r = 4.0 cm away from axis of rotation.

Find:-

(a) Calculate the acceleration of the seed, assuming that it does not slip. (b) What is the minimum value of the coefficient of static friction between the seed and the turntable if the seed is not to slip

Solution:-

- First determine the angular speed (w) of the turntable.

                   w = 2π*N / 60

                   w = 2π*33 / 60

                   w = 3.456 rad/s

- The watermelon seed undergoes a centripetal acceleration ( α ) defined by:

                   α = w^2 * r

                   α = 3.456^2 * 0.04

                   α = 0.477 m / s^2

- The minimum friction force (Ff) is proportional to the contact force of the seed.

- The weight (W) of the seed with mass m acts downwards. The contact force (N) can be determined from static condition of seed in vertical direction.

                   N - W = 0

                   N = W = m*g

- The friction force of the (Ff) is directed towards the center of axis of rotation, while the centripetal force acts in opposite direction. The frictional force Ff = u*N = u*m*g must be enough to match the centripetal force exerted by the turntable on the seed.

                    Ff = m*a

                    u*m*g = m*a

                    u = a / g

                    u = 0.477 / 9.81

                    u = 0.04862

8 0
3 years ago
A plane wave has equation; y= 25sin(120 _4x).find the: (1)wave length (2)wave velocity (3)frequency and period of the wave
kupik [55]

(1) The wavelength of the wave is 1.57 m.

(2) The velocity of the wave is 30 m/s .

(3) The frequency of the wave is 19.10 Hz and the time period of the    wave is 0.052 s.

Note: The given equation seems to be incomplete. Most probably the equation was y=25sin(120t-4x). And the standard system of units (i.e. kg, m, s) is used.

Wavelength: The distance between the consecutive crest or trough of a wave is called the wavelength of a wave.

The equation of a plane wave oscillating in the y direction and traveling in the x direction is given by the equation,

y=A sin(ωt-kx)

where y is the displacement along the y direction, A is the amplitude of the wave, ω is the angular frequency, t is the time, x is the displacement along the x direction, and k is the wave constant.

The given equation is,

y=25sin(120t-4x)

Comparing this equation with the above equation, following values are obtained.

k= 4 m^(-1)

ω =120 rad/s

A=25

The wavelength λ is given by the formula,

λ=2π/k

Here k = 4 m^(-1), so

λ=2π/4

λ=1.57 m.

Velocity: The velocity of a wave is the product of the frequency and the wavelength.

The velocity v is given by the formula,

v=ω*λ/2π

Here ω=120 rad/s and λ=1.57 m, so

v=120*1.57/2π

v=30 m/s

Frequency: The number of oscillations completed in one second is called the frequency of a wave.

The formula of the frequency is,

f=v/λ

Here v=30 m/s and λ=1.57 m, so

f=30/1.57

f=19.10 Hz

Time period: The time taken to complete one cycle of oscillation is called the time period of oscillation.

The formula to calculate the time period T is,

T=2π/ω

Here ω=120 rad/s, so

T=2π/120

T=0.052 s.

Learn more about velocity of wave.

brainly.com/question/25847786

#SPJ4

8 0
2 years ago
Which type of wave would actually slow down when moving from the air into the ocean?
kvasek [131]
Any electromagnetic wave, like light or heat.
5 0
3 years ago
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Will the velocity of the book change as it moves across the surface with NO friction? Explain your answer.
MakcuM [25]

No velocity will not be changed

Why?

According to Newtons 1st law the velocity of a moving object remains unchanged unless a external force affect that.

6 0
3 years ago
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Calculate the change in length of concrete sidewalk (coefficient of linear expansion for concrete is 12*10^-6/celcius) that is 1
anyanavicka [17]

Answer:

The answer to your question is 5.4 cm

Explanation:

This problem refers to calculate the change in length in one dimension due to a change in temperature.

Data

α = 12 x 10⁻⁶

Lo = 150 meters

ΔT = 30 °C

Formula

                    ΔL/Lo = αΔT

solve for ΔL

                    ΔL = αLoΔT

Substitution

                    ΔL = (12 x 10⁻⁶)(150)(30)

Simplification

                    ΔL = 0054 m = 5.4 cm

7 0
3 years ago
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