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Juliette [100K]
2 years ago
8

It is observed that the time for the ball to strike the ground at b is 2.5 s. determine the speed at which the ball was thrown.

Physics
1 answer:
Alika [10]2 years ago
6 0
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A speedboat is moving at a rate of 45 km per hour travels a distance of 27 km. How long did it take to go to 27 km.
8090 [49]

Answer:

I think it is 1.67

Explanation:

I multiply the 45 and 27 cause it says rate of which means to multiply.

8 0
2 years ago
The equation for distance is d = st. If a car has a speed of 85 m/s and travels
Ludmilka [50]

Answer:

D) 10 200 m

Explanation:

Speed is known as the rate of change of distance.

speed=\frac{distance}{time}

distance = speed * time

              = 85 ms⁻¹  * 120 s

              = 10200 m

4 0
2 years ago
A wooden rod of negligible mass and length 84.0 cm is pivoted about a horizontal axis through its center. A white rat with mass
Mandarinka [93]

Answer:

v = 2.029 m/s

Explanation:

Given

L = 84.0 cm   ⇒  R = 0.5*L = 0.5*84 cm = 42 cm = 0.42 m

m₁ = 0.600 kg

m₂ = 0.200 kg

g = 9.8 m/s²

u₁ = u₂ = 0 m/s

v₁ = ?

v₂ = ?

Due to gravity, the bar oscillates and becomes vertical. The mass that occupies the lower position is the one with the highest torque. The one that reduces the potential energy (the system tends to the position of minimum energy). This is achieved if the mass that goes down is 0.6kg (that goes down 42cm) and the one that goes up is 0.2kg (goes up 42cm).

In this system mechanical energy is conserved, so we can match its value in the horizontal position with the one in the vertical.

then

Ei = Ki + Ui = 0.5*(m₁+m₂)*(0)² + (m₁+m₂)*9.8*(0) = 0 J

Ef = Kf + Uf

⇒ Kf = 0.5*(m₁+m₂)*v² = 0.5*(0.6+0.2)*v² = 0.4*v²

⇒ Uf = m₁*g*h₁ + m₂*g*h₂ = 0.6*9.8*(-0.42) + 0.2*9.8*0.42 = - 1.6464

⇒ Ef = Kf + Uf = 0.4*v² - 1.6464

Since

0 = 0.4*v² - 1.6464  ⇒  v = 2.029 m/s

v is the same value due to the wooden rod is pivoted about a horizontal axis through its center and the masses are on opposite ends.

v₁ = v₂ = v    ⇒  ω₁*R₁ = ω₂*R₂  ⇒ ω₁*R = ω₂*R  ⇒ ω₁ = ω₂ = ω

⇒ v = ω*R

5 0
3 years ago
A sled of mass m is being pulled horizontally by a constant horizontal force of magnitude F. The coefficient of kinetic friction
rusak2 [61]

I'll bite:

-- Since the sled's mass is 'm', its weight is 'mg'.

-- Since the coefficient of kinetic friction is μk, the force acting opposite to the direction it's sliding is    (μk) times (mg) .

-- If the pulling force is constant 'F', then the horizontal forces on the sled
are 'F' forward and (μk · mg) backwards.

-- The net force on the sled is  (F - μk·mg).
(I regret the visual appearance that's beginning to emerge,
but let's forge onward.)

-- The sled's horizontal acceleration is  (net force) / (mass) = (F - μk·mg) / m.
This could be simplified, but let's not just yet.

-- Starting from rest, the sled moves a distance 's' during time 't'.
We know that  s = 1/2 a t² , and we know what 'a' is.  So we can write

           s = (1/2 t²)  (F - μk·mg) / m    .

Now we have the distance, and the constant force.
The total work is (Force x distance), and the power is (Work / time).
Let's put it together and see how ugly it becomes.  Maybe THEN
it can be simplified.

Work = (Force x distance) =  F x  (1/2 t²)  (F - μk·mg) / m
 
Power = (Work / time) =    <em>F (t/2) (F - μk·mg) / m </em>

Unless I can come up with something a lot simpler, that's the answer.


To simplify and beautify, make the partial fractions out of the
2nd parentheses:
                                   <em> F (t/2) (F/m - μk·m)</em>

I think that's about as far as you can go.  I tried some other presentations,
and didn't find anything that's much simpler.

Five points,ehhh ?


4 0
2 years ago
Read 2 more answers
In a thermostat, what property of the bimetallic coil allows it to contract and expand? The two metals absorb different amounts
Reika [66]
Hello!

In a thermostat, the property of the bimetallic coil that allows it to contract and expand is that The two metals absorb different amounts of thermal energy. 

This bimetallic coil is used to transform thermal energy into mechanical movement. Two metals with different thermal expansivity are joined together parallelly and the changes of temperature cause bending in different directions depending on if the temperature is rising or descending. 

The differences in the thermal energy absorption of the two metals are the basis for the mechanism of this device. 
3 0
3 years ago
Read 2 more answers
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