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3 years ago

A force of gravity pulls downward on a book on a table. What force prevents the book from accelerating downward?

Physics

2 answers:

Nadusha1986 [10]3 years ago

3 0

Answer: The Normal Force

Explanation:

According to Third Newton's Law, also konwn as The principle of action and reaction :

<em>"If a body A exerts an action on another body B, it performs on A another action that is the same and in the opposite direction."</em>

In this case this is what happens with the book on a table, gravity force pulls it downward, but the Normal Force (perpendicular to the surface of the table) acts in the opposite direction with the same magnitude, preventing the book from accelerating downward.

Gnoma [55]3 years ago

3 0

Answer: The support / normal force

Explanation: The force that prevents downward acceleration is the support force.

The force that acts on the book at rest balancing up the gravitational force is the normal force.

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One horse is pulling a 755 kg sled straight ahead applying a force of 1988 N. If the acceleration of the sled is 1.36 m/s2, what

Inessa [10]

Answer:

The coefficient of kinetic friction is 0.13

Explanation:

Newton's second law states that the acceleration of an object is proportional to the net force on it, the factor of proportionality is the mass. So, we can express that law mathematically as:

$\sum\overrightarrow{F}=m\overrightarrow{a}$ (1)

With F the net force, m the mass and a the acceleration of the object. In our case we're interested on what's happening to the sled, then we have to analyze the forces on it, those forces are the weight and the normal force on the vertical direction and the pulling force and frictional force in the horizontal direction. So, because (1) is a vector equation we can express that in their vertical (y) and horizontal (x) components:

$F_y=ma_y$ (2)

$F_x=ma_x$ (3)

On y we have that the acceleration is zero because the sled is not moving upward or downward, remember that the net force on y is the weight (W) pointing downward and the normal force pointing upward:

$F_y=W+n=0$

Following the convention that positive is upward and negative downward, W=mg=(755)(-9.81):

$F_y=(755)(-9.81)+n=0$

$n=7406.55 N$ (4)

Now on the x direction we have the sum of the forces is the pulling force (T) and friction force (f)

$F_x=F+f=ma_x$

Choosing the direction where the horse is pulling F=1988N and the acceleration should be positive too, then:

$1988+f=m(1.36)$

$f=(755)(1.36)-1988=-961.2 N$

The negative sign means it's in the opposite direction the horse is pulling

The frictional force is related with the coefficient of kinetic friction in the next way:

$|f|=\mu_k n$

with μk the coefficient of kinetic friction, and n the normal force that we already found on (4), so we simply solve the last equation for μk:

$\mu_k=\frac{|f|}{n}=\frac{961.2}{7406.55}=0.13$

4 0

4 years ago

What is the name given to the initial 150 counts in 2 minutes?

Whitepunk [10]

Divide CFU of Dilution. Divide the CFU of the dilution (the number of colonies you counted) by the result from step 4. For this example, you work out 46 ÷ 1/1000, which is the same as 46 x 1,000. The result is 46,000 CFU in the original sample.

7 0

3 years ago

Please help me

g100num [7]

Answer:

0.3956

Explanation:

Newton's 2nd law of motion says that Force = Mass*Acceleration (f=ma) so to find the force used on the football you multiply it's mass by its acceleration.

0.43*0.92 = 0.3956.

0.4 if you round

5 0

3 years ago

The ratio of the focal length of a lens to it's diameter is the

user100 [1]

Answer:

The f-ratio describes the relationship between the lens diameter and the focal length and is calculated by dividing the focal length by the diameter of the lens. For example, if a lens were to have a focal length of 50mm and a diameter of 10mm, then the f-ratio would be 50mm/10mm=5 or otherwise referred to as f5.

Explanation:

6 0

3 years ago

Read 2 more answers

You are at a friend’s house and they show you a magic trick. The balloon when brought near tiny pieces of paper is making the li

andrew11 [14]

Answer:

Static electricity.

Explanation:

Electric Charge; Is the quantity of electricity held in an object

The balloon is electrically neutral, meaning it had an equal amount of positive and negative charges hence it couldn't attract the paper.

After rubbing the balloon, it gained an electric charge; and after gaining this charge it got the ability to exert a force on the pieces of paper and attract them, This is called static electricity.

Therefore, Static electricity caused the paper to stick to the balloon.

5 0

3 years ago