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3 years ago

Which statement is not true?

Physics

2 answers:

Valentin [98]3 years ago

5 0

Answer:

correct answer is objects that are good absorbers of radiation are good reflectors as well

Explanation:

This is a contradiction because good absorbers are poor reflectors. For example if you have a mirror which have shiny surface then it can reflect the radiation in a well manner but it is not a good absorber.

other options are true.

love history [14]3 years ago

4 0

Answer:

A) objects that are good absorbs of radiation are good reflectors as well

Explanation:

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A skill set is explicitly taught or an activity is completed

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3 years ago

What color of light can plants "see"?

mars1129 [50]

As you know, plants are usually green, which means that most other colors are absorbed. One of the most common pigments is called chlorophyll, and one of the varieties is responsible for the green color of plants; it strongly absorbs blue and redlight, which leaves only the green light to make it to our eyes.

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2 years ago

a bullet moving with a velocity of 100m/s pierce a block of wood and moves out with a velocityof 10 m/s.if the thickness of the

erma4kov [3.2K]

The emerging velocity of the bullet is 71 m/s.

The bullet of mass m moving with a velocity u has kinetic energy. When it pierces the block of wood, the block exerts a force of friction on the bullet. As the bullet passes through the block, work is done against the resistive forces exerted on the bullet by the block. This results in the reduction of the bullet's kinetic energy. The bullet has a speed v when it emerges from the block.

If the block exerts a resistive force F on the bullet and the thickness of the block is x then, the work done by the resistive force is given by,

$W=Fx$

This is equal to the change in the bullet's kinetic energy.

$W=Fx=\frac{1}{2} m(u^2-v^2)......(1)$

If the thickness of the block is reduced by one-half, the bullet emerges out with a velocity v₁.

Assuming the same resistive forces to act on the bullet,

$F(\frac{x}{2} )=\frac{1}{2} m(u^2-v_1^2)......(2)$

Divide equation (2) by equation (1) and simplify for v₁.

$\frac{\frac{Fx}{2} }{Fx} =\frac{(u^2-v_1^2)}{(u^2-v^2)} \\\frac{100^2-v_1^2}{100^2-10^2} =\frac{1}{2} \\v_1^2=5050\\v_1=71.06 m/s$

Thus the speed of the bullet is 71 m/s

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3 years ago

A caterpillar crawls 20 feet in 5 minutes. What is the caterpillars crawling speed?

Pavel [41]

The equation is
s= d/t

In this case you would have to write it out as:
s= 20/5
Speed = 4

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3 years ago

The crankshaft in a race car goes from rest to 3000 rpm in 2.0 s.

a_sh-v [17]

The equations are analogous to that for linear movement:
acceleration = (final velocity - initial velocity) / time
acceleration = (3000 rpm - 0 rpm) / 2.0 s
a) acceleration = 1500 rpm/s or 25 rp(s^2)
For the displacement
displacement = initial velocity*time + 0.5*acceleration*time^2
displacement = (0)*(2 s) + (0.5)(25 rps^2)*(2 s)^2
b) displacement = 50 revolutions

3 0

2 years ago

Read 2 more answers