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yaroslaw [1]
3 years ago
10

Which of the following is a good example of a physical change?

Physics
1 answer:
den301095 [7]3 years ago
5 0
Candle burning because it’s going from a solid to a liquid

Plz give me a good mark
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Which statements describe the energy in a food web? Select three options.
hichkok12 [17]

Answer:

it loses engry  it follows difernt paths

Explanation:

8 0
3 years ago
.A hard rubber ball, released at chest height, falls to the pavement and bounces back to nearly the same height. When it is in c
ohaa [14]

Answer:

 a = 1.1 10⁵ m / s²

Explanation:

This is a momentum exercise, where we use the relationship between momentum and momentum

          I = ∫ F dt = Δp

= p_f - p₀

as they indicate that the ball bounces at the same height, we can assume that the moment when it reaches the ground is equal to the moment when it bounces, but in the opposite direction

        F t = 2 (m v)

therefore the average force is

         F = 2 m v / t

where in general the mass of the ball unknown, the velocity of the ball can be calculated using the conservation of energy

starting point. Done the ball is released with zero initial velocity

        Em₀ = U = mgh

final point. Upon reaching the ground, just before the deformation begins

        Em_f = K = ½ m v²

energy is conserved in this system

        Em₀ = Em_f

        m g h = ½ m v²

        v = √ (2gh)

This is the velocity of the body when it reaches the ground, so the force remains

        F = 2m √(2gh)   /t

where the height of the person's chest is known and the time that the impact with the floor lasts must be estimated in general is of the order of milli seconds

knowing this force let's use Newton's second law

          F = m a

          a = F / m

 

          a = 2 √(2gh) / t

We can estimate the order of magnitude of this acceleration, assuming the person's chest height of h = 1.5 m and a collision time of t = 1 10⁻³ s

         a = 2 √ (2 9.8 1.5) / 10⁻³

         a = 1.1 10⁵ m / s²

6 0
3 years ago
What describes how fast an object is moving and in what direction
Mashcka [7]

Speed is a description of how fast an object moves; velocity is how fast and in what direction it moves. In physics, velocity is speed in a given direction. When we say a car travels at 60 km/h, we are specifying its speed.

6 0
3 years ago
Read 2 more answers
1. An electric iron has a rating of 750W, 220V. Calculate:
horrorfan [7]
The equation for electrical power is<span>P=VI</span>where V is the voltage and I is the current. This can be rearranged to solve for I in 6(a). 6(b) can be solved with Ohm's Law<span>V=IR</span>or if you'd like, from power, after substituting Ohm's law in for I<span>P=<span><span>V2</span>R</span></span> For 7, realize that because they are in parallel, their voltages are the same. We can find the resistance of each lamp from<span>P=<span><span>V2</span>R</span></span>Then the equivalent resistance as<span><span>1<span>R∗</span></span>=<span>1<span>R1</span></span>+<span>1<span>R2</span></span></span>Then the total power as<span><span>Pt</span>=<span><span>V2</span><span>R∗</span></span></span>However, this will reveal that (with a bit of algebra)<span><span>Pt</span>=<span>P1</span>+<span>P2</span></span> For 8, again the resistance can be found as<span>P=<span><span>V2</span>R</span></span>The energy usage is simply<span><span>E=P⋅t</span></span>
6 0
3 years ago
A. Draw four rays parallel to the optical axis of your mirror. Two above the optic axis and two below it.
Katen [24]

Answer:

   f = q

Explanation:

In the attachment we can see a diagram of the parallel rays.

The dotted line represents the normal to the mirror surface

These rays when reflected using the constructor equation

        \frac{1}{f} = \frac{1}{p} + \frac{1}{q}

where p and q are the distance to the object and the image respectively.

Since the rays are parallel P = inf

          1 / f = 1 / inf + 1 / q

          f = q

this means that all the rays focus on one focal point.

6 0
3 years ago
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