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katrin2010 [14]
3 years ago
14

A turnip is dropped from a height of 70 meters. How long does it take to hit the ground?

Physics
1 answer:
Bess [88]3 years ago
3 0

Here's a formula for the distance an object falls from rest:

D = (1/2) A T² ... <== MEMORIZE THIS

Distance = (1/2) · (acceleration) · (time²)

On Earth, the acceleration of gravity is always 9.8 m/s².  So for a fall that starts with zero speed, the formula says

70 m = (1/2) (9.8 m/s²) (time²)

70 m = (4.9 m/s²) (time²)

Divide each side by  (4.9 m/s²) ;

time² = (70 m) / (4.9 m/s²)

time² = (70/4.9) sec²

time = √(70/4.9)  seconds

time = 3.78 seconds

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Problem 3: Thermal expansionThe steel rod has the length 2 m and cross-section area 200 cm2at the room temperature 20◦C. Weapply
zalisa [80]

Answer:

a) 2.00024 m

b) 0.036%

c) 436.67°C

Explanation:

Given

Initial length = L₀ = 2 m

Initial cross sectional Area = A₀ = 200 cm² = 0.02 m²

We can obtain initial volume = V₀ = A₀L₀ = 0.02 × 2 = 0.04 m³

Initial Temperature = T₀ = 20°C

Coefficient of linear expansivity = α = (2 × 10⁻⁶) (°C)⁻¹

a) New length of the rod after heating to 80°C

Linear expansion is given as

ΔL = L₀ × α ×ΔT

ΔL = 2 × 2 × 10⁻⁶ × (80 - 20) = 0.00024 m = 0.24 mm

New length = old length + expansion = 2 + 0.00024 = 2.00024 m

b) The percentage of the volume change of the rod.

Volume expansion is given by

ΔV = V₀ × (3α) × ΔT

Volume expansivity ≈ 3 × (linear expansivity)

ΔV = 0.04 × (3×2×10⁻⁶) × (80 - 20) = 0.0000144 m³

Percentage change in volume = 100% × (ΔV/V₀) = 100% × (0.0000144/0.04) = 0.036%

c) The maximal temperature we can allow if the volume should not increase by more than half percent.

For a half percent increase in volume, the corresponding change in volume needs to be first calculated.

Percentage change in volume = 100% × (ΔV/V₀)

0.5 = 100% × (ΔV/0.04)

(ΔV/0.04) = 0.005

ΔV = 0.0002 m³

Then we now investigate the corresponding temperature that causes this.

ΔV = V₀ × (3α) × ΔT

0.0002 = 0.04 × (3×2×10⁻⁶) × ΔT

ΔT = (0.0002)/(0.04 × 3 × 2 × 10⁻⁶) = 416.67°C

Maximal temperature = T₀ + ΔT = 20 + 416.67 = 436.67°C

4 0
3 years ago
Witch of the following is the correct definition of convention
iogann1982 [59]

Answer:

A is the answer .(A) is correct

3 0
2 years ago
Which is an example of action and reaction forces?
Vlad [161]

Hey there!

the answer is

C. a tennis racket striking a tennis ball

Thank you

Best regards

           OFFICIALLYSAVAGE2003

7 0
3 years ago
Read 2 more answers
Tsunamis are fast-moving waves often generated by underwater earthquakes. In the deep ocean their amplitude is barely noticable,
Andrei [34K]

Answer:

a) V = 195.70 m/s

b) f=3.02 × 10⁻⁴ Hz

c) T = 3311.25 seconds

Explanation:

Given:

Wavelength, λ = 646 Km = 646000 m

Distance traveled = 3410 Km = 3410000 m

Time = 4.84 h = 4.84 × 3600 s = 17424 seconds

a) The speed (V) of the wave is given as

V = distance / time

V = 3410000 m/ 17424 seconds

or

V = 195.70 m/s

b) The frequency (f) of the wave is given as:

f = V / λ

f= 195.70 / 646000

f=3.02 × 10⁻⁴ Hz

c) The time period (T)  is given as:

T = 1/ f

T = 1/ (3.02 × 10⁻⁴) Hz

T = 3311.25 seconds

5 0
3 years ago
two negative charges that are both -3.0 C push each other apart with a force of 19.2 N how far apart are the charges
Hoochie [10]
The electrostatic force between two charges q1 and q2 is given by
F=k_e  \frac{q_1 q_2}{r^2}
where k_e =8.99 \cdot 10^9 N m^2 C^{-2} is the Coulomb's constant and r is the distance between the two charges.

If we use F=19.2 N and q1=q2=-3.0 C, we can find the value of r, the  distance between the two charges by re-arranging the previous formula:
r= \sqrt{k_e \frac{q_1 q_2}{F} }= \sqrt{ 8.99 \cdot 10^9 N m^2 C^{-2} \frac{(-3.0C)^2}{19.2 N} } =6.49 \cdot 10^4 m=64.9 km
5 0
3 years ago
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