Physics Middle School

## Answers

**Answer 1**

Answer: The formula used to calculate speed is distance divided by time.

Explanation:

Speed is defined as the rate of change of distance with respect to time.

The equation used to calculate speed of the object follows:

The S.I. unit of speed is meters per second (m/s)

For Example: A car traveled a distance of 200 meters in 5 second.

Hence, the formula used to calculate speed is distance divided by time.

## Related Questions

A 1,000 kg ball traveling at 5 m/s would have kinetic energy

### Answers

Answer:

12500 J = 12.5 kJ

Explanation:

Kinetic energy is the energy possessed by a moving object solely due to its motion.

You can get the K.E. of an object using the equation,

K.E. = (1/2)mv²

So you get, for ball

K.E. = (1/2)×1000×5² = 12500 J = 12.5 kJ

A 50.0 kg piece of rock slides down the side of Mt. Etna. That part of the volcano slopes up at 30.0° (from the horizontal). If the rock accelerates at 3.0 m/s2, what is the coefficient of friction between the rock and the volcano?

### Answers

Answer:

0.224

Explanation:

There are two forces acting on the rock along the direction parallel to the slope:

- The component of the weight parallel to the slope, down, given by

where

m = 50.0 kg is the mass of the rock

is the acceleration of gravity

is the angle of the slope

- The force of friction, up along the slope, given by

where

is the coefficient of friction

R is the normal reaction

So the equation of the forces along the direction parallel to the slope is

(1)

where

is the acceleration

The normal reaction R can be found by looking at the equation of the forces along the direction perpendicular to the slope: in fact, we have that R balances the component of the weight perpendicular to the slope, so

And substituting into (1)

And solving for , we find the coefficient of friction:

What is the relationship between gravity and mass?

### Answers

Answer:

Gravity is the attraction between two objects that have mass. The amount of gravity is directly proportional to the amount of mass of the objects and inversely proportional to the square of the distance between the objects. Gravity is a force that increases the velocity of falling objects - they accelerate.

Explanation:

Determine the average spacing between cars of a row proceeding at 60 km/h, if the driver of a car travelling

at 80 km/h in the opposite direction passes by 14 cars

of the row per kilometre. (The average length of the

cars is 5 m.)

### Answers

Average spacing between cars of a row =

Explanation:

Let us assume the average spacing between cars to be .

Frame of Reference : Frame attached to Cars moving at .

In this frame, the cars in the row are at rest, while the car travelling in opposite direction appears to move at a relative speed of .

He is covering a distance of in ground frame. His speed in ground frame is . So, time taken to traverse 1 km is

In this T time, he moves in the relative frame at . The distance covered in relative frame will be

×

×

It passes 14 cars while traversing this distance.

∴ 14 ×

×

.

∴Average Spacing betwwen cars in a row =

How do trees help to reduce the speed of moving air

### Answers

Answer:

they block it with their branches

Explanation:

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Est. Length: 2:00:00

Steven Thomas: Attempt 1

Answer both parts of this essay question:

A) (5pts) Describe the mass, charge, and location of protons, neutrons, and electrons

in an atom.

B) (6pts) How do protons, neutrons, and electrons determine the properties of an

atom (what is the ROLE of each particle)?

### Answers

Answer: (A) protons and neutrons both have a mass of 1 amu and are found in the nucleus. However, protons have a charge of positive 1, and neutrons are uncharged. Electrons have a mass of approximately 0 amu, orbit the nucleus, and have a charge of negative 1.

(B) The number of electrons, in turn, determines the chemical properties of the atom. Protons contribute to the mass of an atom and provide the positive charge to the nucleus. The number of protons also determines the identity of the element. Electrons have a negative charge

Explanation:

What is an incandescent light bulb, how does it work and how much does it cost?

### Answers

Explanation:

An incandescent bulb works by heating a filament in the bulb at high temperatures such that it produces it glows and produces visible light. The filament, usually a thin tungsten metal, heats up by imposing a high resistance to electric current. High resistance builds up heat in the filament causing it to glow. The bulb is filled with inert gases- like neon or halogen- to prevent oxidation of the filament.

The price of an incandescent bulb is approximately $21.

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A 20 N force causes an impulse of 500 N*s. How long was the force applied for?

### Answers

Answer:

25sec

Explanation:

Impulse = Force * time (period)

therefore,

500N*s= 20N * x(secs)

divide both sides by 20

results in 500/20=x

x= 25 secs

What is the relationship between the masses of the objects and the gravitational force between them

### Answers

The relationship between the masses of the object and the gravitational force between them is a direct relationship

Explanation:

The gravitational force between two objects is given by the equation:

where

is the gravitational constant

m1, m2 are the masses of the two objects

r is the separation between them

We observe that:

- The gravitational force is proportional to the masses of the two objects, m1 and m2, so if the masses increase, the force will increase as well (so, this is a direct relationship)

- The gravitational force is inversely proportional to the square of the separation between the objects, so if the distance is increased, the force will decrease (so, this is an inverse relationship)

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A person walks 6 m East, 9m North, 2 m South, 1 m West, and then 3 m North

### Answers

Answer:

From their original location, they are 5m east and 10m North.

S/He should then cool the muscles down gradually, then shower completely, dress in clean clothing and clean, dry socks, take in fluids and some protein, and get adequate sleep at the end of the day.

A call to Mother would also be a nice gesture.

A train has an acceleration of magnitude 0.90 m/s2 while stopping. A pendulum with a 0.55-kg bob is attached to a ceiling of one of the cars. Determine the angle that the pendulum makes with the vertical during the decceleration of the train

### Answers

The angle of the pendulum with the vertical is

Explanation:

As the train decelerates, the bob of the pendulum will feel a force given by

where

m = 0.55 kg is the mass of the bob

is the magnitude of the acceleration

In the horizontal direction.

The pendulum will be inclined at an angle from the vertical, so it will be in equilibrium, and therefore the horizontal component of the tension in the string must be equal to the net force F of the previous equation:

(1)

where T is the tension in the string.

We also know that the bob is in equilibrium along the vertical direction: so the vertical component of the tension must be equal to the weight of the bob,

(2)

where is the acceleration of gravity.

Dividing eq.(1) by eq(2), we get:

And therefore, we find the angle:

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What is an example of reflection? a.)A jet plane creating a sonic boom

b.(A straw appearing bent in water

c.)A sound wave echoing in a valley

d.)A sound wave traveling around a

corner

### Answers

A sound wave echoing in a valley

The sound waves are being reflected across the valley walls, thus producing an echo

Answer:A

Explanation:

A 5.0 kg box is sliding across a waxed floor by the application of a 15 N east force. If the force of friction is 2.5 N west, what is the net force acting on the box? Whis is the box's acceleration

### Answers

1) 12.5 N east

There are two forces acting on the box along the horizontal direction:

- The applied force of 15 N east, we indicate it with F

- The force of friction of 2.5 N west, we indicate it with

Taking east as positive direction, we can write the two forces has

Therefore, the net force on the box will be:

And the positive sign means the direction is east.

2)

We can solve this part by using Newton's second law:

where

is the net force on the box

m is its mass

a is the acceleration

For the box in this problem,

(east)

m = 5.0 kg

Solving for a, we find the acceleration:

And the direction is the same as the net force (east)

4) A car traveling at 10 m/sec rolls off the edge of a cliff. The cliff is 37.6 m above the ocean. How far from the base of the cliff does the car strike the water?

### Answers

The car strikes the water 27.7 m far from the base of the cliff

Explanation:

The motion of the car is a projectile motion. it follows a parabolic path which consists of two independent motions:

- A uniform motion (constant velocity) along the horizontal direction

- An accelerated motion with constant acceleration (acceleration of gravity) in the vertical direction.

First, we consider the vertical motion. Since this is a free fall motion, we can use the following suvat equation to find the time of flight of the car:

where:

s = 37.6 m is the vertical displacement (the height of the cliff)

u = 0 is the initial vertical velocity of the car

t is the time of flight

is the acceleration of gravity (choosing downward as positive direction)

Solving for t, we find:

Now we use the horizontal motion. This is a uniform motion at constant speed, so the horizontal distance travelled by the car is given by:

where:

is the initial horizontal velocity (which is constant)

t = 2.77 s is the time of flight

Solving for d:

So, the car strikes the water 27.7 m far from the base of the cliff.

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Calculate the distance (in km) you travel it you maintain an average speed

10 km/hr for 1/2 hour.

### Answers

Answer:

5 km

Explanation:

For a uniform motion, the relationship between distance, time and speed is:

where

d is the distancee travelled

t is the time taken

v is the average speed

In this problem,

v = 10 km/h

t = 1/2 h = 0.5 h

Therefore, the distance travelled is

A ball is projected 203 meters straight upward and then falls the same distance back to its starting point. Neglecting air resistance, its total time in the air is about.

### Answers

Answer:

12.88 s

Explanation:

We can solve this problem by considering only the first half the motion, from the moment the ball is projected upward to the moment it reaches its maximum height.

Since this is a uniformly accelerated motion, we can use the following suvat equation:

where:

s is the vertical displacement

v is the final velocity

t is the time

a is the acceleration

Here we have:

v = 0: the vertical velocity is zero when the ball has reached its maximum height, that is

s = 203 m

(acceleration of gravity, negative because it is downward)

Solving the equation for t, we find the time at which the ball reaches the maximum height:

The second half of the motion is symmetrical and identical to the first one, so the total time in air is just twice this time, therefore:

An 80-kg astronaut becomes separated from his spaceship. He is 15.0 m away from it and at rest relative to it. In an effort to get back, he throws a 500 gram object with a speed of 8.0 m/s in a direction away from the ship. How long does it take him to get back to the ship?

### Answers

The astronaut will take 300 seconds

Explanation:

We can solve this problem by using the law of conservation of momentum.

In fact, the total momentum of the astronaut+object system must be conserved.

Initially, they are both at rest, so their total momentum is zero:

After the astronaut throws the object, their total momentum is:

where:

M = 80 kg is the mass of the astronaut

V is the final velocity of the astronaut

m = 500 g = 0.5 kg is the mass of the object

v = 8.0 m/s is the velocity of the object

Since momentum is conserved, we can write

And solving for V,

Which means that he starts moving at 0.05 m/s in the direction opposite to the object.

Now the astronaut needs to cover a distance of

d = 15.0 m

And his speed is

v = 0.05 m/s

Therefore, the time taken is

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if you throw a ball straight up into the air at a velocity of 15 m/s you want to know how high above your hand the ball will be at exactly 2.5 sec after you released it

### Answers

Answer:

Assuming that gravity has not caused the ball to start falling then after 2.5 seconds the ball will be 37.5 meters in the air

Explanation:

The ball travels 15 meters every second so for 2 seconds we would multiply 15*2=30. We have 2.5 seconds so to calculate the time traveled in half a second we would divide 15/2=7.5

Then we add 30+7.5= 37.5 meters

Which two element are most likely in the same group

### Answers

The answer would be Bismuth and Nitrogen because they have the same number of valence electrons. Groups in the periodic table are arranged in columns. When it comes to neutral atoms, the number of valence electrons it has is equal to the main group of that element.

An 80-kg astronaut becomes separated from his spaceship. He is 15.0 m away from it and at rest relative to it. In an effort to get back, he throws a 500 gram object with a speed of 8.0 m/s in a direction away from the ship. How long does it take him to get back to the ship?

### Answers

Answer: 300 s

Explanation:

The momentum is given by the following equation:

Where is the mass of the object and is the velocity.

In addition, according to the conservation of linear momentum, we have:

(1)

Where:

is the initial momentum of the astronaut, which is initially at rest

is the final momentum, being , and

Then (1) is rewritten as:

(2)

Finding te velocity of the astronaut :

(3)

(4)

(5) The negative sign of the velocity indicates it is directed towards the spaceship, however its speed (the magnitude of the velocity vector) is positive

On the other hand we have the following:

(6)

Where the distance between the astronaut and the spacheship and the time. So, we have to find :

(7)

Finally: