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mel-nik [20]
3 years ago
6

A construction worker dropped a brick from a high scaffolding. How fast was? a. How fast was the brick moving after 4.0 s of fal

ling? b. How far did the brick fall after 4.0 s of falling?
Physics
1 answer:
Zigmanuir [339]3 years ago
5 0
A) How fast was the brick moving after 4s?
Vf=?
Vi=0 (because it was dropped, not thrown)
A= -9.8m/s^2 (gravity)
t= 4s
Use the equation Vf=Vi+A(t)
Vf=0+(-9.8)(4)
Final answer: Vf= -39.2m/s
b) How far did the brick fall after 4s?
D=?
Vi=0
t=4s
A=-9.8m/s2
**You do have the final velocity, but it is best to avoid using numbers that you have calculated yourself.**
Use the equation: d=Vi(t)+0.5(A)(t)^2
d=(0)(4)+0.5(-9.8)(4)^2
d=(-4.9)(16)
d=-78.4m
Therefore, after 4s the brick fell 78.4m
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You are standing next to a table and looking down on a record player sitting on the table. Take the spindle (axis of rotation) t
VLD [36.1K]

Answer:

a) the rotational speed of the clay is  3.45 rad/s

b) the value of A in the equation of motion is 0.15 m

c) the value of ϕi is 90° or π/2 rad.

Explanation:

 Given that;

Revolution per minute rpm = 33( 1/3) =  100/3

The frequency f = 100 / 3(60) = 0.55 Hz

a)

Rotational speed W = 2πf

we substitute

W = 2π × 0.55

W = 3.45 rad/s

Therefore, the rotational speed of the clay is  3.45 rad/s

b)

given equation; y(t)=Asin(ωt+ϕi)

given that radius = 0.15 m

y(t)=(0.2)sin(ωt+ϕi)

Therefore, the value of A in the equation of motion is 0.15 m

c)

since y(t) has the maximum value at t =0

so at t=0

y(0) = (0.15)sin(ω(0)+ϕi)

= 0.15sin(ϕi)

this will give maximum value when ϕi = 90°

so

y(0) = (0.15)sin(ω(0)+ϕi)

= 0.15sin(90°)

= 0.15

hence, the value of ϕi is 90° or π/2 rad.

7 0
2 years ago
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kykrilka [37]

Answer:

I think the Bulb No. 2 will stop emitting light if the bulb No. 1 burns out.

3 0
3 years ago
it takes 90 j of work to stretch a spring 0.2 m from its equilibrium position. How muc work is needed to stretch it an additiona
Vinvika [58]

Work needed: 720 J

Explanation:

The work needed to stretch a spring is equal to the elastic potential energy stored in the spring when it is stretched, which is given by

E=\frac{1}{2}kx^2

where

k is the spring constant

x is the stretching of the spring from the equilibrium position

In this problem, we have

E = 90 J (work done to stretch the spring)

x = 0.2 m (stretching)

Therefore, the spring constant is

k=\frac{2E}{x^2}=\frac{2(90)}{(0.2)^2}=4500 N/m

Now we can find what is the work done to stretch the spring by an additional 0.4 m, that means to a total displacement of

x = 0.2 + 0.4 = 0.6 m

Substituting,

E'=\frac{1}{2}kx^2=\frac{1}{2}(4500)(0.6)^2=810 J

Therefore, the additional work needed is

\Delta E=E'-E=810-90=720 J

Learn more about work:

brainly.com/question/6763771

brainly.com/question/6443626

#LearnwithBrainly

7 0
3 years ago
Hey help me plzzzzz i will mark brainliest​
vodomira [7]

Answer:

The answer to your question is given below.

Explanation:

Mechanical advantage (MA) = Load (L)/Effort (E)

MA = L/E

Velocity ratio (VR) = Distance moved by load (l) / Distance moved by effort (e)

VR = l/e

Efficiency = work done by machine (Wd) /work put into the machine (Wp) x 100

Efficiency = Wd/Wp x100

Recall:

Work = Force x distance

Therefore,

Work done by machine (wd) = load (L) x distance (l)

Wd = L x l

Work put into the machine (Wp) = effort (E) x distance (e)

Wp = E x e

Note: the load and effort are measured in Newton (N), while the distance is measured in metre (m)

Efficiency = Wd/Wp x100

Efficiency = (L x l) / (E x e) x 100

Rearrange

Efficiency = L/E ÷ l/e x 100

But:

MA = L/E

VR = l/e

Therefore,

Efficiency = L/E ÷ l/e x 100

Efficiency = MA ÷ VR x 100

Efficiency = MA / VR x 100

7 0
3 years ago
Wrapping paper is being unwrapped from a 5.0-cm radius tube, free to rotate on its axis. if it is pulled at the constant rate of
lisov135 [29]
So the equation for angular velocity is

Omega = 2(3.14)/T

Where T is the total period in which the cylinder completes one revolution.

In order to find T, the tangential velocity is

V = 2(3.14)r/T

When calculated, I got V = 3.14

When you enter that into the angular velocity equation, you should get 2m/s
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3 years ago
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