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ad-work [718]
2 years ago
10

Using the standard convention "positive is up", what is the sign of the acceleration of a rock you throw up (a) as it is going u

p, and (b) as it is coming back down?
Physics
1 answer:
Sonbull [250]2 years ago
7 0

Answer:

(a) Negative

(b) Positive

Explanation:

Here is a question on sign.

(a) When the rock is going up, it is working against gravity. In this case, the acceleration due to gravity will take a negative value. This is because gravity works or acts downwards

(b) When the rock is coming down, it is actually working with gravity. So in this case, the sign will ne positive

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An object of mass m travels along the parabola yequalsx squared with a constant speed of 5 ​units/sec. What is the force on the
Dmitriy789 [7]

Explanation:

The object is moving along the parabola y = x² and is at the point (√2, 2).  Because the object is changing directions, it has a centripetal acceleration towards the center of the circle of curvature.

First, we need to find the radius of curvature.  This is given by the equation:

R = [1 + (y')²]^(³/₂) / |y"|

y' = 2x and y" = 2:

R = [1 + (2x)²]^(³/₂) / |2|

R = (1 + 4x²)^(³/₂) / 2

At x = √2:

R = (1 + 4(√2)²)^(³/₂) / 2

R = (9)^(³/₂) / 2

R = 27 / 2

R = 13.5

So the centripetal force is:

F = m v² / r

F = m (5)² / 13.5

F = 1.85 m

7 0
3 years ago
What is the gravitational force between a 45 kg person, and the Earth at 5.98 x 1024 kg, with a distance of
Assoli18 [71]

Answer:

C. 441 N

Explanation:

Gravitational force between two objects can by calculated by the formula

= G m₁m₂ / r² , m₁ and m₂ are masses at distance r

= ( 6.67 x 10⁻¹¹ x 45 x 5.98 x 10²⁴) / ( 6.38 x 10⁶ )²

= 44.09 x 10

= 440.9 N

= 441 N .  

7 0
3 years ago
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
3 years ago
2. Use physics terms to explain the benefits of crumple zones in modern cars.
Elden [556K]

Answer:

They decrease trauma by allowing for a more gradual change in velocity

Explanation:

6 0
3 years ago
22. Explain why it is better to increase the biodiversity of ecosystem.
Marizza181 [45]

Answer: because increasing biodiversity can influence ecosystem functions such as productivity and variety and even the likelihood that a particular species is discovered by a comminity

Explanation:

7 0
3 years ago
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