If the treadmill’s initial speed is 1.7m/s, what will its final speed be?

A cement block accidentally falls from rest from the ledge of a 52.9-m-high building. When the block is 14.3 m above the ground,

Anna007 [38]

Answer:

The man has at most 0.418 secs to get out of the way

Explanation:

To determine how much time at most the man has to get out of the way, we will calculate the time it will take the block to reach height 1.94m from height 14.3m.

To do this, we will first determine the time it will take the block to reach height 1.94 m from height 52.9 m and find the time it takes the block to reach height 14.3m above the ground from the same height (52.9 m), the difference is the time the man has to get out of the way.

Now, the time it will take the block to reach height 1.94 m from height 52.9 m

This means the time it will take the block to travel a height distance of 52.9m - 1.94m = 50.96m

From one of the equations of motions for free falling bodies

h = ut + 1/2(gt²)

Where h is the height

u is the initial velocity

t is the time

and g is the acceleration due to gravity (Take g = 9.8 m/s²)

From the question, the block falls from rest

∴ u = 0 m/s

h = 50.96 m

Putting these into the equation

50.96 = 0(t) + 1/2(9.8)(t²)

50.96 = 4.9t²

t² = 50.96/4.9

t² = 10.4

t = √10.4

t = 3.225 secs

This is the time it will take to reach height 1.94m (that is to reach the man)

For the time it takes the block to reach height 14.3m above the ground from height 52.9 m

That is, the time it takes the block to travel a height distance of 52.9m - 14.3m = 38.6 m

Here,

h = 38.6 m

and u = 0 m/s

Putting these into the same equation

h = ut + 1/2(gt²)

38.6 = 0(t) + 1/2(9.8)(t²)

38.6 = 4.9t²

t² = 38.6/4.9

t² = 7.878

t = √7.878

t = 2.807 secs

This is the time it takes the block to reach height 14.3 m

Now, the difference in time is 3.225secs - 2.807 secs = 0.418 secs

Hence, the man has at most 0.418 secs to get out of the way.

7 0

3 years ago

The metric unit of force is the

grandymaker [24]

The unit of force is the 'Newton'.

1 newton is the force that accelerates 1 kilogram of mass
at the rate of 1 meter per second-squared.

1 N = 1 kg-m/s²

-- A force of 1 pound is about 4.448 newtons.

-- A force of 1 newton is about 3.6 ounces.

6 0

3 years ago

Read 2 more answers

Please help fast!!

daser333 [38]

The answer is C..........

4 0

3 years ago

You have a string with a mass of 0.0133 kg. You stretch the string with a force of 8.89 N, giving it a length of 1.97 m. Then, y

Kazeer [188]

Answer:

(i) The wavelength is 0.985 m

(ii) The frequency of the wave is 36.84 Hz

Explanation:

Given;

mass of the string, m = 0.0133 kg

tensional force on the string, T = 8.89 N

length of the string, L = 1.97 m

Velocity of the wave is:

$V = \sqrt{\frac{F_T}{M/L} } \\\\V = \sqrt{\frac{8.89}{0.0133/1.97} } \ = 36.29 \ m/s$

(i) The wavelength:

Fourth harmonic of a string with two nodes, the wavelength is given as,

L = 2λ

λ = L/2

λ = 1.97 / 2

λ = 0.985 m

(ii) Frequency of the wave is:

v = fλ

f = v / λ

f = 36.29 / 0.985

f = 36.84 Hz

3 0

3 years ago

Air contained in a rigid, insulated tank fitted with a paddle wheel, initially at 300 K, 2 bar, and a volume of 3 m3, is stirred

madam [21]

Answer:

a)P₂ =4 bar

b)W= - 1482.48 KJ

It means that work done on the system.

c)S₂ - S₁ = 3.42 KJ/K

Explanation:

Given that

T₁ = 300 K ,V₁ = 3 m³ ,P₁=2 bar

T₂ = 600 K ,V₂=V₁ 3 m³

Given that tank is rigid and insulated.It means that volume of the gas will remain constant.

Lets take the final pressure = P₂

For ideal gas P V = m R T

$\dfrac{P_2}{P_1}=\dfrac{T_2}{T_1}$

$P_2=\dfrac{T_2}{T_1}\times P_1$

$P_2=\dfrac{600}{300}\times 2$

P₂ =4 bar

Internal energy

ΔU = m Cv ΔT

Cv=0.71 KJ/kg.k for air

$m=\dfrac{PV}{RT}$

$m=\dfrac{200\times 3}{0.287\times 300}\ kg$

m= 6.96 kg

ΔU= 6.96 x 0.71 x (600 - 300)

ΔU=1482.48 KJ

From first law

Q= ΔU + W

Q= 0 Insulated

W = - ΔU

W= - 1482.48 KJ

It means that work done on the system.

Change in the entropy

$S_2-S_1=mC_v\ \ln\dfrac{T_2}{T_1}$

$S_2-S_1=6.96\times 0.71\ \ln\dfrac{600}{300}$

S₂ - S₁ = 3.42 KJ/K

5 0

3 years ago