Convert 45 kg to unit mg

According to Jean Piaget, in what stage of cognitive development are children able to understand conservation tasks?

Virty [35]

Answer:

Preoperational

Explanation:

According to Piaget's theory of cognitive development, the preoperational stage is the second stage. This stage includes children between the age group of 2 to 7 years. Children can understand conservation tasks and learn to manipulate various symbols during this stage.

So, the answer is the preoperational stage.

8 0

3 years ago

Charlie throws a ball up into the air. While the ball is airborne, which is the greatest force acting on the ball to slow it dow

oksian1 [2.3K]

I believe it is the gravitational force for gravity controls the speed of the object hurdling towards the ground.

3 0

3 years ago

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which of the following temperatures is the lowest? A.100C) B.100F) C.100K) or D. they are all the same

KonstantinChe [14]

Answer:

100 degrees Celsius is the highest temperature. 100F is 37.8 C and 310.7K. 100C is 237.6F and 373K. 100K is -173C and -253.8F. So 100C is the highest temperature.

pls mark brainliest

5 0

3 years ago

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URGENT. Physics quiz on force, distance, etc. will reward brainliest.

goblinko [34]

13a) 9 J

The work done is equal to the area under the curve between x=0 cm and x=30 cm. However, first we should find the magnitude of the force for x=30 cm. If we notice that the force is proportional to the stretching x, we can set the following proportion to find the value of F for x=30 cm:

$10 N : 5 cm = x : 30 cm$

$x=\frac{30 cm \cdot 10 N}{5 cm}=60 N$

And so, the work done is

$W=Area=\frac{1}{2}(base)(height)=\frac{1}{2}(0.30 m)(60 N)=9 J$

13b) 24.5 m/s

The kinetic energy gained by the arrow is equal to the work done in stretching the bow:

$K=W=9 J$

Given the formula for the kinetic energy:

$K=\frac{1}{2}mv^2$

we can find the speed v of the arrow:

$v=\sqrt{\frac{2K}{m}}=\sqrt{\frac{2\cdot 9J}{0.030 kg}}=24.5 m/s$

13c) 30.6 m

If shot vertically upward, at the point of maximum height all the initial kinetic energy of the arrow is converted into gravitational potential energy:

$\frac{1}{2}mv^2 = mgh$

Re-arranging the formula and using the initial speed of the arrow, we can find its maximum height h:

$h=\frac{v^2}{2g}=\frac{(24.5 m/s)^2}{2(9.81 m/s^2)}=30.6 m$

14) 20 m/s

We can solve the problem by using the work-energy theorem. In fact, the work done by the frictional force of the brake is equal to the change in kinetic energy of the car:

$W=\Delta K=K_f -K_i$

$Fd=\frac{1}{2}mv^2-\frac{1}{2}mu^2$

where

$F=-2500 N$ is the force applied by the brakes (with a negative sign, since it is opposite to the displacement of the car)

$d=100 m$ is the displacement of the car

$m=1000 kg$ is the car's mass

$v$ is the final speed of the car

$u=30 m/s$ is the initial speed of the car

By re-arranging the equation, we can find v:

$v=\sqrt{\frac{2(Fd+\frac{1}{2}mu^2)}{m}}=20 m/s$

15) 5.0 m/s

We can solve the problem by using the law of conservation of energy:

$U_i + K_i = U_f + K_f\\mgh_i + \frac{1}{2}mu^2 = mgh_f + \frac{1}{2}mv^2$

where

m is the mass of the pendulum

$h_i=1.2 m$ is the initial height of the pendulum

$u=3 m/s$ is the initial speed of the pendulum

$h_f=0.4 m$ is the final height of the pendulum

$v$ is the final speed of the pendulum

Re-arranging the equation, we can find v:

$v=\sqrt{2gh_i + u^2 - 2gh_f}=5.0 m/s$

16) Point B (at the top of the loop)

Gravitational potential energy is defined as:

$U=mgh$

where m is the mass, g is the gravitational acceleration and h is the height above the ground. Therefore, we see that the potential energy is proportional to h: the higher the ball above the ground, the greater its potential energy. In this example, the point of maximum height is point B, therefore it is the point where the ball has the largest potential energy.

17) Law of conservation of energy: the total mechanical energy of an isolated object is conserved (if no frictional force act on it)

Example: A stone left falling from rest from a cliff. Let's call h the height of the cliff, m the mass of the stone. The mechanical energy of the stone is constant, and it is sum of the potential energy and kinetic energy:

$E=U+K$

At the top of the cliff, the kinetic energy is zero (the stone is at rest), so all its energy is potential energy:

$E_i = U_i = mgh$

When the stone falls, its energy is converted into kinetic energy. Just before hitting the ground, the height has become zero, h=0, so the potential energy is zero and all the mechanical energy is now kinetic energy:

$E_f=K_f=\frac{1}{2}mv^2$

since the mechanical energy must be conserved, we can write

$E_i=E_f\\mgh = \frac{1}{2}mv^2\\2gh=v^2$

6 0

4 years ago

how much power is needed to lift a box with a force of 780 newtons over a distance of 2 meters in 45 seconds

-BARSIC- [3]

Answer:

Explanation:

Power is the rate at which work is done and can be found by using the formula

$p = \frac{w}{t} \\$

p is the power in Watts (W)

w is the workdone in joules

t is time in s

but workdone = force × distance

From the question

force = 780 N

distance = 2 m

workdone = 780 × 2 = 1560 N

Since we now have the value of workdone we can find the power

We have

$p = \frac{1560}{45} = 34.6666666... \\$

We have the final answer as

Hope this helps you

3 0

3 years ago