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ra1l [238]
4 years ago
7

A strong-armed physics student throws a tennis ball vertically. The ball stays in the air for 5.5 seconds. Assuming the ball lef

t from the ground, how fast did it leave his hand?
Physics
1 answer:
Mila [183]4 years ago
4 0

Answer:

27.5 m/s

Explanation:

applying motion equations we can find the answer,

v = u + a*t

Let assume ,

u = starting speed(velocity)

v = Final speed (velocity)

t =  time taken for the motion

a = acceleration

by the time of reaching the highest point subjected to the gravity , the speed should be equal to zero  (only a vertical speed component is there)

for the complete motion it takes 5.5 s. that means to reach the highest point it will take 5.5/2 =2.75 seconds

we consider the motion upwards , in this case the gravitational  acceleration should be negative in upwards (assume g=10 m/s2)

that is,

v = 0 , a = -10ms^{-2}    , t =2.75

v = u + at

0 = u -10*2.75

u = 27.5 ms^{-1}

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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
Two coulombs of charge pass through a wire in 5 seconds. Calculate the current in the wire. 1​
gogolik [260]

Answer:

0.4A.

Explanation:

Current (A) = Charge (coulomb)/Time (secs)

2 coulombs/5 secs = 0.4A

7 0
3 years ago
How do you label acceleration, momentum, speed, force, and velocity?
Akimi4 [234]
I have a a work sheet to do and i have choices for the diffrent words, 
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<span>B:s </span>
<span>C:m/s </span>
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3 0
4 years ago
A short-wave radio antenna is supported by two guy wires, 155 ft and 175 ft long. Each wire is attached to the top of the antenn
Vladimir79 [104]

Answer:

163.8 ft

Explanation:

In triangle ABD

AB = 155 ft

Cos63 = \frac{BD}{AB} = \frac{BD}{155}\\BD = 155 Cos63 \\BD = 70.4 ft

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Using Pythagorean theorem in triangle ADC

AC^{2} = AD^{2} + DC^{2} \\175^{2} = 148^{2} + DC^{2} \\DC = 93.4 ft

d = distance between the anchor points

distance between the anchor points is given as

d = BD + CD = 70.4 + 93.4\\d = 163.8 ft

5 0
4 years ago
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balu736 [363]

Answer:

carpet

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The structure of carpet's surface is as shown. Thus it shows large amount of diffuse reflection.

4 0
3 years ago
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