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dexar [7]
2 years ago
14

In the past, most children who went sledding in the winter snow in Verland used wooden sleds with runners and steering bars. Ten

years ago, smooth plastic sleds became popular; they go faster than wooden sleds but are harder to steer and slow. The concern that plastic sleds are more dangerous is clearly borne out by the fact that the number of children injured while sledding was much higher last winter than it was ten years ago.
Which of the following, if true in Verland, most seriously undermines the force of the evidence cited?
(A) A few children still use traditional wooden sleds.
(B) Very few children wear any kind of protective gear, such as helmets, while sledding.
(C) Plastic sleds can be used in a much wider variety of snow conditions than wooden sleds can.
(D) Most sledding injuries occur when a sled collides with a tree, a rock, or another sled.
(E) Because the traditional wooden sled can carry more than one rider, an accident involving a wooden sled can result in several children being injured.
Physics
1 answer:
Dovator [93]2 years ago
3 0

Answer:

(E) it seems like the best option

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Simon is riding a bike at 12 km/h away from his friend Keesha.He throws a ball at 5 km/h back to Keesha, who is standing still o
Tems11 [23]

I notice that even though we're working with frames of reference
here, you never said which frame the '5 km/hr' is measured in.

In fact !  You didn't even say which frame the '12 km/hr' of his
bike is measured in.

So there are several different ways this could go.  I'll do it the way
I THINK you meant it, but that doesn't guarantee anything.

-- Simon is riding his bike at 12 km/hr relative to the sidewalk,
away from Keesha.

-- He throws a ball at Keesha, at 5 km/hr relative to his own face.

-- Keesha sees the ball approaching her at (12 - 5) = 7 km/hr
relative to the ground and to her.

5 0
3 years ago
If there is an object in top of another object, why does the upper object exert a downward normal force?​
rusak2 [61]

Answer:

This is because normal force is exerted perpendicularly to the point of contact between the upper and lower objects.  

Explanation:

This is because the upper object is still subject to gravitational pull. Therefore, the amount of force it exerts on the lower object due to gravity will be equal to the normal force that acts in the negative direction of gravitational force. Additionally, normal force is evident because the upper object will not go into the lower object.

4 0
3 years ago
g The potential energy of a pair of hydrogen atoms separated by a large distance x is given by U(x)=−C6/x6, where C6 is a positi
Arisa [49]

Answer:

F_x = -\frac{6 C_6}{2^7}

Attractive

Explanation:

Data provided in the question

The potential energy of a pair of hydrogen atoms given by \frac{C_6}{X_6}

Based on the given information, the force that one atom exerts on the other is

Potential energy μ = \frac{C_6}{X_6}

Force exerted by one atom upon another

F_x = \frac{\partial U}{\partial X} = \frac{\partial}{\partial X}  (-\frac{C_6}{X^6})

or

F_x = \frac{\partial}{\partial X}  (\frac{C_6}{X^6})

or

F_x = -\frac{6 C_6}{2^7}

As we can see that the C_6 comes in positive and constant which represents that the force is negative that means the force is attractive in nature

5 0
3 years ago
The end diastolic volume of a heart is 140 mL Assume that it is a sphere. At end diastole, the intraventricular pressure is 7mmI
Vera_Pavlovna [14]

Answer:

Explanation:

We know that, V = 140 mL = 0.00014 m3

Assume that it is a sphere. so, we have

V = (4/3) \pir3

r3 = (0.00014 m3) (3) / (4) (3.14)

r = \sqrt[3]{}\sqrt[3]{}3\sqrt{}3.34 x 10-5 m3

r = 1.93 x 10-7 m

(a) The wall tension at end diastole will be given as :

using a formula, we have

T = P r / 2 H

where, P = intraventricular pressure at end diastole = 7 mmHg = 933.2 Pa

H = wall thickness at this time = 0.011 m

then, we get

T = (933.2 Pa) (1.93 x 10-7 m) / 2 (0.011 m)

T = 8.18 x 10-3 N

(b) The wall tension at the end of isovolumetric contraction will be given as :

using a formula, we have

T = P r / 2 H

where, P = intraventricular pressure at end of isovolumetric contraction = 80 mmHg = 10665.7 Pa

H = wall thickness at this time = 0.011 m

then, we get

T = (10665.7 Pa) (1.93 x 10-7 m) / 2 (0.011 m)

T = 9.35 x 10-2 N

(d) The wall stress from A and B which will be given as :

we know that, \sigma = T / w

For part A, we have

\sigmaA = (8.18 x 10-3 N) / (0.011 m)

\sigmaA = 0.743 N/m

For part B, we have

\sigmaB = (9.35 x 10-2 N) / (0.011 m)

\sigmaB = 8.5 N/m

4 0
3 years ago
Based on Newton’s 3rd Law of motion, if an archer shoots an arrow at the target, the action force is the bowstring against the a
maw [93]

Answer:

maybe target, not sure.

6 0
3 years ago
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