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nalin [4]
3 years ago
9

A ball is thrown from a hot air balloon that is at rest 245 m above the ground. How long will it take for the ball to reach the

ground? How fast will the ball be traveling when it reaches the ground?
Physics
1 answer:
tino4ka555 [31]3 years ago
5 0

Answer:

7.07 s

69.3 m/s

Explanation:

Taking the negative direction to be down and the positive direction to be up:

We have 3 variables in the y-direction and can solve for time.

  • v₀ = 0 m/s
  • a = -9/8 m/s²
  • Δy = -245 m
  • t = ?

Use this kinematics equation to solve for time.

  • Δx = v₀t + 1/2at²
  • -245 = 1/2(-9.8)t²
  • -245 = -4.9t²
  • t² = 50
  • t = 7.07106781187

It will take the ball 7.07 s to reach the ground.

We can solve for final velocity using the same variables in the y-direction:

  • v₀ = 0 m/s
  • a = -9/8 m/s²
  • Δy = -245 m  
  • v = ?

Use this kinematics equation to solve for final velocity.

  • v² = v₀² + 2aΔx
  • v² = 2(-9.8)(-245)
  • v² = 4802
  • v = 69.2964645563

The ball will be traveling at a speed of 69.3 m/s at the instant before it reaches the ground.

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A stationary speed gun emits a microwave beam at 2.10*10^10Hz. It reflects off a car and returns 1030 Hz higher. What is the spe
KIM [24]

Answer: V = 15 m/s

Explanation:

As  stationary speed gun emits a microwave beam at 2.10*10^10Hz. It reflects off a car and returns 1030 Hz higher. The observed frequency the car will be experiencing will be addition of the two frequency. That is,

F = 2.1 × 10^10 + 1030 = 2.100000103×10^10Hz

Using doppler effect formula

F = C/ ( C - V) × f

Where

F = observed frequency

f = source frequency

C = speed of light = 3×10^8

V = speed of the car

Substitute all the parameters into the formula

2.100000103×10^10 = 3×10^8/(3×10^8 -V) × 2.1×10^10

2.100000103×10^10/2.1×10^10 = 3×108/(3×10^8 - V)

1.000000049 = 3×10^8/(3×10^8 - V)

Cross multiply

300000014.7 - 1.000000049V = 3×10^8

Collect the like terms

1.000000049V = 14.71429

Make V the subject of formula

V = 14.71429/1.000000049

V = 14.7 m/s

The speed of the car is 15 m/s approximately.

8 0
3 years ago
Help please 20 points ? ASAP
KengaRu [80]

Answer:

21: Mass

22: Unbalanced Force

23: Friction

24: Balanced

Explanation:

3 0
3 years ago
Two subway stops are separated by 1210 m. If a subway train accelerates at 1.30 m/s2 from rest through the first half of the dis
solong [7]

Answer:

Part 1) Time of travel equals 61 seconds

Part 2) Maximum speed equals 39.66 m/s.

Explanation:

The final speed of the train when it completes half of it's journey is given by third equation of kinematics as

v^{2}=u^2+2as

where

'v' is the final speed

'u' is initial speed

'a' is acceleration of the body

's' is the distance covered

Applying the given values we get

v^2=0+2\times 1.30\times \frac{1210}{2}\\\\v^{2}=1573\\\\\therefore v=39.66m/s

Now the time taken to attain the above velocity can be calculated by the first equation of kinematics as

v=u+at\\\\v=0+1.30\times t\\\\\therefore t=\frac{39.66}{1.30}=30.51seconds

Since the deceleration is same as acceleration hence the time to stop in the same distance shall be equal to the time taken to accelerate the first half of distance

Thus total time of journey equalsT=2\times 30.51\approx61seconds

Part b)

the maximum speed is reached at the point when the train ends it's acceleration thus the maximum speed reached by the train equals 39.66m/s

4 0
4 years ago
PLEASE HELP ASAP!!! CORRECT ANSWER ONLY PLEASE!!!
Natasha_Volkova [10]

Ok srry bout last time but the answer is A) kelvin: time the reason is because everything else is a SI. Hope this helps and TURTLE

7 0
3 years ago
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Give two reasons why circular water waves decrease in amplitude
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1. friction between water molecules
2. the wave spreads out onto a larger and larger area, so per unit area, the energy of the wave goes down
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