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3 years ago

You throw a ball straight up. You are extra strong feeling today. It takes 11 seconds for the ball to come back down.

Physics

1 answer:

ollegr [7]3 years ago

5 0

Answer:

A. 148.23 m

B. 2.75 m/s

Explanation:

The following data were obtained from the question:

Time of flight (T) = 11 s

Maximum height (h) =?

Initial velocity (u) =?

Next, we shall determine the time taken for the ball to get to the maximum height. This can be obtained as follow:

Time of flight (T) = 11 s

Time (t) to reach the maximum height =.?

T = 2t

11 = 2t

Divide both side by 2

t = 11/2

t = 5.5 s

NOTE: Time to reach the maximum height is the same as the time taken for the ball to fall back to the plane of projection.

A. Determination of the maximum height to which the ball was thrown.

Time (t) to reach maximum height = 5.5 s

Acceleration due to gravity (g) = 9.8 m/s²

Maximum height (h) =?

h = ½gt²

h = ½ × 9.8 × 5.5²

h = 4.9 × 30.25

h = 148.23 m

B. Determination of the initial velocity.

Maximum height (h) reached = 148.23 m

Acceleration due to gravity (g) = 9.8 m/s²

Initial velocity (u) =?

u² = h/2g

u² = 148.23 / (2 × 9.8)

u² = 148.23 / 19.6

Take the square root of both side

u = √(148.23 / 19.6)

u = 2.75 m/s

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A merry-go-round with a rotational inertia of 600 kg m2 and a radius of 3.0 m is initially at rest. A 20 kg boy approaches the m

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Answer:

The velocity of the merry-go-round after the boy hops on the merry-go-round is 1.5 m/s

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The rotational inertia of the merry-go-round = 600 kg·m²

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The speed with which the boy approaches the merry-go-round = 5.0 m/s

$F_T \cdot r = I \cdot \alpha = m \cdot r^2 \cdot \alpha$

Where;

$F_T$ = The tangential force

I = The rotational inertia

m = The mass

α = The angular acceleration

r = The radius of the merry-go-round

For the merry go round, we have;

$I_m \cdot \alpha_m = I_m \cdot \dfrac{v_m}{r \cdot t}$

$I_m$ = The rotational inertia of the merry-go-round

$\alpha _m$ = The angular acceleration of the merry-go-round

$v _m$ = The linear velocity of the merry-go-round

t = The time of motion

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$I_b \cdot \alpha_b = m_b \cdot r^2 \cdot \dfrac{v_b}{r \cdot t}$

Where;

$I_b$ = The rotational inertia of the boy

$\alpha _b$ = The angular acceleration of the boy

$v _b$ = The linear velocity of the boy

t = The time of motion

When the boy jumps on the merry-go-round, we have;

$I_m \cdot \dfrac{v_m}{r \cdot t} = m_b \cdot r^2 \cdot \dfrac{v_b}{r \cdot t}$

Which gives;

$v_m = \dfrac{m_b \cdot r^2 \cdot \dfrac{v_b}{r \cdot t} \cdot r \cdot t}{I_m} = \dfrac{m_b \cdot r^2 \cdot v_b}{I_m}$

From which we have;

$v_m = \dfrac{20 \times 3^2 \times 5}{600} = 1.5$

The velocity of the merry-go-round, $v_m$ , after the boy hops on the merry-go-round = 1.5 m/s.

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Explanation:

We will use the equations of constant acceleration to find out $a_{x}$ and time t.

As we know that the initial speed is zero. So

(a)

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(c)

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= (9.11× $10^{-31}$ )(4.356× $10^{14}$ m/s²)

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