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nadezda [96]
3 years ago
7

PLEASE HELP An object is thrown upward with an initial velocity of 32.1 m/s. What is its velocity in 4.0 s? (use g = 9.81 m/s2).

Please include step by step process. -7.14 11.2 7.14 -4.6
Physics
1 answer:
grigory [225]3 years ago
6 0

Answer:

-7.14

Explanation:

According to equation of motion

v = u + at

where

v is the final velocity at any time t

u is the initial velocity

a is the acceleration

and t is the time

___________________________________________

Given

An object is thrown upward it means

its initial velocity is in upward direction

but acceleration due to gravity is in downward direction which will cause to decrease the velocity of object.

Intial velocity u = 31.1 m/s

final velocity v at 4 second we have to find.

t = 4 second

a = g = 9.81 m/s2 (it is acting in opposite direction of motion hence its sign will be negative ).

Thus

a = -  9.81 m/s2

using the above values in v = u + at

v = 32.1 - 9.81*4

v = 32.1 - 39.24

v = -7.14

Thus, correct option is -7.14.

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Consider an elevator with a table and a book on top of the table. The mass of the table is 10kg and the mass of the book is 2kg.
Step2247 [10]

Newton's second law allows us to find the force of the block on the table is 126 N

Newton's second law says that the net force is proportional to the product of the mass and the acceleration of the body

                Σ F = m a

Where the bold letters indicate vectors, m is the mass and the acceleration of the body

A free body diagram is a diagram where the forces are represented without the details of the bodies, in the attached we can see a free body diagram of the system.

Let's start by finding the acceleration of the elevator with kinematics  

                 v = v₀ + a t

                 a = \frac{v-v_o}{a}  

Where v and v₀ are the current and initial velocity, respectively, at acceleration and t is the time

                 a = \frac{8-1}{2}

                 a = 3.5 m / s²

Let's write Newton's second law for each body

The book

                N₂ - W₂ + N₁ = m a

               

Table

                N₁ - W₁ - W₂ = M a

                W₁ = Mg

                W₂ = mg

                N₁ = (M + m) g + M a

                N₁ = (10 + 2) 9.8 + 10 3.5

                N₁ = 152.6 N

This is the reaction of the earth to the support of the block and the table

               N₂ = ma + m g  - N₁

               N₂ = m ( a +g) - N₁  

               N₂ = 2 (3.5 + 9.8) - 152.6

               N₂ = 26.6 - 152.6

               N₂ = -126 N

The negative sign indicates that the direction is opposite to the one assigned, this is the action of the block on the table.

In conclusion using Newton's second law we can find the forces of the block on the table is 126 N

Learn more here: brainly.com/question/19860811

4 0
2 years ago
A kangaroo jumps straight up to a vertical height of 1.45 m. How long was it in the air before returning to Earth?
dexar [7]

Answer:

1.08 s

Explanation:

From the question given above, the following data were obtained:

Height (h) reached = 1.45 m

Time of flight (T) =?

Next, we shall determine the time taken for the kangaroo to return from the height of 1.45 m. This can be obtained as follow:

Height (h) = 1.45 m

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

Time (t) =?

h = ½gt²

1.45 = ½ × 9.8 × t²

1.45 = 4.9 × t²

Divide both side by 4.9

t² = 1.45/4.9

Take the square root of both side

t = √(1.45/4.9)

t = 0.54 s

Note: the time taken to fall from the height(1.45m) is the same as the time taken for the kangaroo to get to the height(1.45 m).

Finally, we shall determine the total time spent by the kangaroo before returning to the earth. This can be obtained as follow:

Time (t) taken to reach the height = 0.54 s

Time of flight (T) =?

T = 2t

T = 2 × 0.54

T = 1.08 s

Therefore, it will take the kangaroo 1.08 s to return to the earth.

3 0
3 years ago
The "Biltmore Agreement" stipulated that a. remote broadcasts could not emanate from hotels. b. NBC could not give away tickets
Anna35 [415]

Answer:

The "Biltmore Agreement" stipulated that:

Radio stations agreed to broadcast no longer than five minutes of news, twice per day, while using information supplied by the newspapers.

e. radio stations could only air five-minutes newscasts a day.

Explanation:

The Biltmore Agreement tried to reconcile within the press war between newspapers and radio, as during its golden age the newspapers´ revenues decreased. Radio´s brand new technology was more attractive and creative for advertising and could report breaking news faster than the newspapers, which through the press associations including the Associated Press and the United Press, pressured to stop providing news to radio stations beginning a war in 1933, which partially ended with the Biltmore Agreement, which restricted the radio´s broadcasting of news if the newspapers continued publishing radio listings, radio stations were to broadcast no longer than five minutes of news, twice per day, if information supplied by the newspapers was used, no sponsors were allowed, and no more that 30 words in a single story were allowed either;  radio stations had to include: "See your daily newspaper for further details" in their announcements and, could only broadcast news after 9:30 AM for morning news, and after 9:00 PM for evening news, so people would have already received their newspapers.

7 0
3 years ago
Calculate the acceleration of a bus that goes
Svet_ta [14]

The acceleration of the bus is 1.11 meters per second square to the direction of motion

Explanation:

Acceleration is the rate of change of velocity

The formula of the acceleration is a=\frac{v_{2}-v_{1}}{t} , where

  • v_{1} is the initial velocity
  • v_{2} is the final velocity
  • t is the time

A bus that goes  from 10 km/h to a speed of 50 km/h in 10 seconds

→ v_{1} = 10 km/h

→ v_{2} = 50 km/h

→ t = 10 seconds

Change the unite of the time from seconds to hour

→ 1 hour = 60 × 60 = 3600 seconds

→ 10 seconds = \frac{10}{3600}=\frac{1}{360} hour

Substitute these values in the formula of the acceleration above

→ a=\frac{50-10}{\frac{1}{360}}

→ a = 14400 km/h²

To change the unit of acceleration to meter per second change the

  kilometer to meter and the hour to seconds

→ 1 km = 1000 m

→ 1 hour = 3600 seconds

→ a=\frac{14400*1000}{(3600)^{2}}=\frac{10}{9}

→ a = 1.11 m/sec².

The acceleration of the bus is 1.11 meters per second square to the direction of motion

Learn more:

You can learn more about the acceleration in brainly.com/question/6323625

#LearnwithBrainly

4 0
3 years ago
A 438kg car is accelerating east at 2.55m/s^2. What is the total force acting east on the car
lisabon 2012 [21]

Answer:

<h2>1116.9 N</h2>

Explanation:

The force acting on an object given it's mass and acceleration can be found by using the formula

force = mass × acceleration

From the question we have

force = 438 × 2.55

We have the final answer as

<h3>1116.9 N</h3>

Hope this helps you

5 0
3 years ago
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