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vichka [17]
3 years ago
5

A tennis player standing 12.6 m from the net hits the ball at 3.18° above the horizontal. To clear the net, the ball must rise a

t least 0.362 m. If the ball just clears the net at the apex of its trajectory, how fast was the ball moving when it left the racket?
Physics
1 answer:
SOVA2 [1]3 years ago
3 0
At the vertex, it's vertical velocity is 0, since it has stopped moving up and is about to come back down, and its displacement is 0.33m.
So we use v² = u² + 2as (neat trick I discovered just then for typing the squared sign: hold down alt and type 0178 on ur numpad wtih numlock on!!!) ANYWAY.......
We apply v² = u² + 2as in the y direction only. Ignore x direction.
IN Y DIRECTION:
v² = u² + 2as
0 = u² - 2gh
u = √(2gh) (Sub in values at the very end)
So that will be the velocity in the y direction only. But we're given the angle at which the ball is hit (3° to the horizontal). So to find the velocity (sum of the velocity in x and y direction on impact) we can use: sin 3° = opposite/hypotenuse = (velocity in y direction only) / (velocity)
So rearranging,
velocity = (velocity in y direction only) / sin 3°
= √(2gh)/sin 3°
= (√(2 x 9.8 x 0.33)) / sin 3°
= 49 m/s at 3° to the horizontal
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nignag [31]

Answer:

1. B. The person and the Earth

2. This is because the energy gained by the person equals the energy lost by the earth,

Explanation:

1.

B. The person and the Earth

This is because the person and the earth both represent a system. A system consists of more than one item. A system consists of two or more items interacting with each other.

2. This is because, the energy of an isolated system is conserved according to the second law of thermodynamics which states that in an isolated system, energy can neither be created nor destroyed. So, there is an exchange of energy between the person and the Earth. So, the energy gained by the person at the new height equals the energy lost by the earth. And thus, the total energy of the system remains constant.

6 0
3 years ago
A solid, horizontal cylinder of mass 10.6 kg and radius 1.00 m rotates with an angular speed of 8.00 rad/s about a fixed vertica
n200080 [17]

Answer:

The final angular speed is 7.71 rad/s

Explanation:

Given

Cylinder mass, M = 10.6 kg

Cylinder radius, R = 1.00 m

Angular speed, w = 8.00 rad/s.

Mass of putty, m = 0.250-kg

Radius, r = 0.900 m

First, we set up an expression for the initial and final angular momentum of the system.

The moment of inertia of the cylinder is given as I = ½MR²

While the moment of inertia if the putty is mr².

Initial Momentum of the system = Initial momentum of the cylinder =

Li = Iw --- Substitute ½MR² for I

Li = ½MR²w

By

Substituton

Li = ½ * 10.6 * 1² * 8

Li = 42.4kgm²/s

Calculating the final momentum of the system.

First we calculate the final momentum of the cylinder

Li = Iw --- Substitute ½MR² for I

Li = ½MR²wf where wf = final angular speed

By

Substituton

Li = ½ * 10.6 * 1² wf

Li = 5.3w kgm²/s

Then we calculate the final momentum of the putty

Final Momentum of the putty =

L2 = Iwf --- Substitute mr² for I;

L2 = mr²wf --- By Substituton

L2 = 0.25 * 0.9² * wf

L2 = 0.2025wf kgm²/s

Final momentum = Li + L2

Lf = (5.3wf + 0.2025wf) kgm²/s

Lf = 5.5025wf kgm²/s

By conservation of momentum

Li = Lf

Where Li = 42.4kgm²/s and Lf = 5.5025wf kgm²/s

So, we have

5.5025wf kgm²/s = 42.4kgm²/s --- make wf the subject of formula

wf = 42.4/5.5025

wf = 7.71 rad/s

Hence, the final angular speed is 7.71 rad/s

5 0
3 years ago
Chuck drove 35mi from Austin to San Marcos in 40min, stopped 30min for a hamburger, and then drove 45mi to San Antonio in 50min.
Effectus [21]

Answer:

his average speed was 40 miles per hour

5 0
2 years ago
Which gas is a source of natural groundwater pollution?
Hatshy [7]
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7 0
3 years ago
Two soccer players run toward each other. One player has a mass of 85 kg
sveta [45]

Answer:

Total momentum, p = 55 kg-m/s

It is given that,

Mass of player 1, m₁ = 85 kg

Mass of player 2, m₂ = 105 kg

Speed of player 1, v₁ = -8 m/s (west)

Speed of player 2, v₂ = 7 m/s (east)

Momentum is equal to the product of mass and velocity. For this system, momentum is given by :

p=m_1v_1+m_2v_2p=m

1

v

1

+m

2

v

2

p=85\ kg\times (-8\ m/s)+105\ kg\times 7\ m/sp=85 kg×(−8 m/s)+105 kg×7 m/s

p = 55 kg-m/s

The total momentum of the system made up of the two players is 55 kg-m/s.

8 0
2 years ago
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