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3 years ago

A tennis ball is hit into the air with a racket. When is the ball’s kinetic energy the greatest? Ignore air resistance.

Physics

1 answer:

Lady bird [3.3K]3 years ago

4 0

Answer B is the correct answer

We know that kinetic energy $E = \frac{1}{2} mv^2$ , where m is the mass of object and v is the velocity of object.

In this case only velocity is the variable, mass remains constant.

So point having higher velocity has higher kinetic energy.

When it leaves the racket, the ball will be having a certain height, but just before it reaches the ground it will not having any height. So maximum velocity of ball is at that time when it reaches just above the ground.

So option B is the correct answer.

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The first ionization energy of a hydrogen atom is 2.18 aj (attojoules). what is the frequency and wavelength, in nanometers, of

jasenka [17]

1) Frequency: $3.29\cdot 10^{15}Hz$

the energy of the photon absorbed must be equal to the ionization enegy of the atom, which is

$E=2.18 aJ=2.18\cdot 10^{-18} J$

The energy of a photon is given by

$E=hf$

where $h=6.63\cdot 10^{-34}Js$ is the Planck's constant. By using the energy written above and by re-arranging thsi formula, we can calculate the frequency of the photon:

$f=\frac{E}{h}=\frac{2.18\cdot 10^{-18} J}{6.63\cdot 10^{-34} Js}=3.29\cdot 10^{15} Hz$

2) Wavelength: 91.2 nm

The wavelength of the photon can be found from its frequency, by using the following relationship:

$\lambda=\frac{c}{f}$

where $c=3\cdot 10^8 m/s$ is the speed of light and f is the frequency. Substituting the frequency, we find

$\lambda=\frac{3\cdot 10^8 m/s}{3.29\cdot 10^{15}Hz}=9.12\cdot 10^{-8} m=91.2 nm$

5 0

2 years ago

Complete this sentence. If the mass of object A is __________ than object B, then the weight of object A will be _______________

AfilCa [17]

Answer:

Complete this sentence. If the mass of object A is greater than object B, then the weight of object A will be heavier the weight of object B.

Explanation:

If the mass of Object A is more/greater than object B then it would be "heavier"

4 0

2 years ago

Read 2 more answers

A box of mass 60 kg is at rest on a horizontal floor that has a static coefficient of friction of 0.6 and a kinetic coefficient

gavmur [86]

Answer:

a) The minimum force required to start moving the box is 352.86 N

b) i) The friction force for the box in motion is 147.025 N

ii) The acceleration of box is 4.21625 m/s²

Explanation:

The parameters of the box at rest and the floor are;

The mass of the box = 60 kg

The static coefficient friction of the floor = 0.6

The kinetic coefficient friction of the floor = 0.25

Frictional force = Normal force × Friction coefficient

For an horizontal floor and the box laying on the floor, we have;

The normal force = The weight of the box = Mass of the box × Acceleration due to gravity, g

The acceleration due to gravity, g = 9.81 m/s²

The weight of the box = 60 × 9.81 = 588.6 N

a) The static coefficient gives the frictional force observed by the box and which must be surpassed to bring about motion

Therefore;

The minimum force required to start moving the box = The static frictional force = Weight of the box × The static coefficient of friction

The minimum force required to start moving the box = 588.1 × 0.6 = 352.86 N

The minimum force required to start moving the box = 352.86 N

b) i) When an horizontal force of 400 N is applied, the applied force is larger than the static friction force, and the box will be in motion with the kinetic coefficient of friction being the source of friction

The friction force for the box in motion = 588.1 × 0.25 = 147.025 N

ii) The force, F with the box is in motion, is given as follows;

F = Mass of box × Acceleration of box, a = Applied force - Kinematic friction force

F = 60 × a = 400 - 147.025 = 252.975 N

60 × a = 252.975 N

a = 252.975 N/(60 kg) = 4.21625 m/s²

Acceleration of box, a = 4.21625 m/s².

6 0

2 years ago

Can someone please help me how to set this up?

fiasKO [112]

The car has a 12 mile head start, going 80 mph, so his distance is:dcar=80∗t+12
The is going at 108 mph, so his distance is:dcop=108t
Setting them equal to each other we get:80t+12=108t⇒12=28t⇒t=1228=37
So 3/7 of an hour.about 25.7 mins.

5 0

2 years ago

Read 2 more answers

A 14.0 gauge copper wire of diameter 1.628 mmcarries a current of 14.0 mA. Part A: What is the potential difference across a 2.1

FrozenT [24]

Answer:

for copper potential difference is 2.4871 × $10^{-4}$ V

for silver potential difference is 2.1256 × $10^{-4}$ V

Explanation:

given data

diameter D = 1.628 mm = 0.001628 m

current = 14.0 mA = 0.0140 A

length L = 2.15 m

to find out

potential difference

solution

we consider here

resistivity of silver = 1.47 × $10^{-8}$ ohm-m

resistivity of copper = 1.72 × $10^{-8}$ ohm-m

so we apply here resistance formula that is

Resistance = ρ × L / A ...............1

so here area A = πr² = π(0.001628 /2)² = 2.0816 × $10^{-6}$ m²

for copper Resistance = ρ × L / A

Resistance = 1.72 × $10^{-8}$ × 2.15 / 2.0816 × $10^{-6}$

Resistance = 1.7765 × $10^{-2}$ ohm

for silver Resistance = ρ × L / A

Resistance = 1.47 × $10^{-8}$ × 2.15 / 2.0816 × $10^{-6}$

Resistance = 1.5183 × $10^{-2}$ ohm

potential difference is calculated as

for copper potential difference = current × resistance

potential difference = 0.0140 ×1.7765 × $10^{-2}$

potential difference = 2.4871 × $10^{-4}$ V

for silver potential difference = current × resistance

potential difference = 0.0140 × 1.5183 × $10^{-2}$

potential difference = 2.1256 × $10^{-4}$ V

7 0

2 years ago