For an object to be seen, light must leave _______ and enter ______

A car is traveling at a steady 73 km/h in a 50 km/h zone. A police motorcycle takes off at the instant the car passes it, accele

iVinArrow [24]

Answer:

29 m

Explanation:

given,

speed of the car = 73 Km/hr

= 73 x 0.278 m/s = 20.3 m/s

Time elapses before the motorcycle is moving as fast as the car

using equation of motion

v = u + at

initial speed = 0 m/s

20.3= 0 + 7 x t

t = 2.9 s

b) distance traveled by the car in that time

d = s x t

d = 20.3 x 2.9 = 58.87 m

distance traveled by the police

$s = ut + \dfrac{1}{2} a t^2$

$s = 0 + \dfrac{1}{2}\times 7\times 2.9^2$

s = 29.435 m

distance car is ahead = 58.57 - 29.44 = 29.13

= 29 m

3 0

3 years ago

How many electrons does a neutral atom of sudium-25 have

horrorfan [7]

Answer:

Option A. 11

Explanation:

The atomic number of an element does not change.

Recall:

Atomic number = proton number

If the atom is neutral, then,

Proton number = electron number

Since the element is sodium, then, the atomic number of sodium–25 is 11.

Also, we were told to obtain the electrons of a neutral atom of sodium–25

Therefore,

Atomic number = proton number = 11

Since the atom is neutral,

Proton number = electron number = 11

8 0

3 years ago

Two facing surfaces of two large parallel conducting plates separated by 8.5 cm have uniform surface charge densities such that

elena-s [515]

Answer:

positive plate

E = 5.764 KV / m

W = 490eV or 7.85 * 10^-17 J

E_p = 4.74 *10^(-12) eV

E_k = 490 eV

Explanation:

part a

The potential difference between two plates = 490 V

Distance between two plates = 8.5 cm

Answer: The positive plate is at higher potential because of convention.

part b

Electric Field between the plates

E = V / d

E = 490 / 0.085 = 5.764 KV / m

Answer: Electric Field between the plates E = 5.764 KV / m

part c

Work done by electric field

W = V*q

W = 490 * 1.602*10^-19

W = 7.85 * 10^-17 J

or W = 490 eV

Answer: Work done by electric field W = 490eV or 7.85 * 10^-17 J

part d

Potential Energy of an electron gained:

E_p = m_e * g * d / (1.602*10^-19)

E_p = 9.109*10^-31* 9.81 * 0.085 / (1.602*10^-19)

E_p = 4.74 *10^(-12) eV

Very very small E_p approximately 0

Answer: Potential Energy of an electron gained E_p = 4.74 *10^(-12) eV or 0.

part e

Kinetic Energy of an electron gained:

W - E_p = E_k

E_k = 490eV - 4.74*10^(-12)eV

E_k = 490 eV

Answer: Kinetic Energy of an electron gained E_k = 490 eV

7 0

4 years ago

Alex has to pick up a 20 N stack of documents and raise them 5 meters from the floor.

Serjik [45]

Answer:

1.Work done=100 joules

2.potential energy

3.kinetic energy

Explanation:

W=Force x distance

w= 20 N x 5 M

W = 100 JOULES

6 0

4 years ago

Mary pushes a crate by applying force of 18 newtons. Unable to push it alone, she gets help from her friend, Anne. Together they

maw [93]

<span>This problem is relatively simple, in order to solve this problem the only formula you need to know is the formula for friction, which is:

Ff = UsN

where Us is the coefficient of static friction and N is the normal force.

In order to get the crate moving you must first apply enough force to overcome the static friction:

Fapplied = Ff

Since Fapplied = 43 Newtons:

Fapplied = Ff = 43 = UsN

and it was given that Us = 0.11, so all you have to do is isolate N by dividing both sides by 0.11

43/0.11 = N = 390.9 which is approximately 391 or C. 3.9x10^2</span>

7 0

3 years ago

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For an object to be seen, light must leave _______ and enter _______.

For an object to be seen, light must leave _ and enter _.