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3 years ago

Imagine a box sitting on a shelf. What forces are acting on the box?

1 answer:

8 0

In case of an object sitting at rest on another base, there are two equal and opposite forces – Normal force and the gravity.

Answer: Option A

Explanation:

When an object is placed at rest position on another object, there is a force exerted by the surfaces of the two contact objects. This force is denoted as Normal Force.

When an object such as a box is placed on a shelf, its surface exerts a contact force on the base of the shelf- The Normal force directed upward. Meanwhile, the gravity stays at its action and tries to pull the box towards itself.

Both of these forces however are equal and opposite and therefore, there is zero net force on the box. That's why it remains at rest, holding on Newton's third law.

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A Ferris wheel has diameter of 10 m. It rotates at a uniform rate and makes one revolution in 8.0 seconds. A person weighing 670

Nikolay [14]

Answer: 459.14 N

Explanation:

from the question, we have

diameter = 10 m

radius (r) = 5 m

weight (Fw) = 670 N

time (t) = 8 seconds

Circular motion has centripetal force and acceleration pointing perpendicular and inwards of the path, therefore we apply the equation below

∑ F = F c = F w − Fn ..............equation 1

Fn = Fw − Fc = mg − (mv^2 / r) ...................equation 2

substituting the value of v as (2πr / T) we now have

Fn = mg − (m(2πr / T )^2) / r

Fn= mg − (4(π^2)mr / T^2) ..........equation 3

Fw (mass of the person) = mg

therefore m = Fw / g

m = 670 / 9.8 = 68.367 kg

now substituting our values into equation 3

Fn = 670 - ( (4 x (π^2) x 68.367 x 5 ) / 8^2)

Fn = 670 - 210.86

Fn = 459.14 N

4 0

3 years ago

A 1400-kg car is moving at a speed of 25m/s. how much kinetic energy does the car have?

Luba_88 [7]

Answer:

437.5Kjoules

Explanation:

K.E=half multiply by mass multiply by square of velocity

=437.5Kjoules

3 0

2 years ago

The size of a balloon increases when the pressure inside it increases. The balloon gets bigger when it is left in the heat from

Masteriza [31]

Explanation:

This happens because the gas inside tend to expand because its temperature gets higher.

This is why the balloon that is put in a freezer for too long tend to gets smaller, because the gas temperature that is inside the balloon decreases.

(you can try it at home)

It is related to the temperature of the gas.

5 0

2 years ago

A student at another university repeats the experiment you did in lab. Her target ball is 0.860 m above the floor when it is in

dexar [7]

Answer:

K = 0.076 J

Explanation:

The height of the target, h = 0.860 m

The mass of the steel ball, m = 0.0120 kg

Distance moved, d = 1.50 m

We need to find the kinetic energy (in joules) of the target ball just after it is struck. Let t is the time taken by the ball to reach the ground.

$h=ut+\dfrac{1}{2}at^2\\\\t=\sqrt{\dfrac{2h}{g}}$

Put all the values,

$t=\sqrt{\dfrac{2\times 0.860 }{9.8}} \\\\=0.418\ s$

The velocity of the ball is :

$v=\dfrac{1.5}{0.418}\\\\= $$3.58\ m/s$

The kinetic energy of the ball is :

$K=\dfrac{1}{2}mv^2\\\\K=\dfrac{1}{2}\times 0.0120\times 3.58^2\\\\=0.076\ J$

So, the required kinetic energy is 0.076 J.

6 0

3 years ago

A wave has a wavelength of 7 mm and a frequency of 19 hertz. What is its speed?

ASHA 777 [7]

Speed = (frequency) x (wavelength)

Speed = (19 per second) x (7 mm)

Speed = (19 x 7) (per second · mm)

Speed = 133 mm/sec

or you might want to write Speed = 0.133 m/s .

4 0

3 years ago