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Lilit [14]
4 years ago
9

Janet ran 30 meters in 4 seconds,what is her speed.

Physics
2 answers:
lubasha [3.4K]4 years ago
8 0

Answer:

7.5 meters per second

Explanation:

30 / 4 = 7.5

7.5 * 1 = 7.5

7.5 * 2 = 15

7.5 * 3 = 22.5

7.5 * 4 = 30

MrRa [10]4 years ago
5 0

7.5 i believe it's right.

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______ attract objects made of iron ​
Bess [88]

Answer:

(That an object must be made out of metal to be attracted, but not all metals are attracted.) Metals such as iron, nickel, and cobalt are attracted to magnets. Steel has iron in it, so it is also attracted to magnets.

Explanation:

basically magnets

8 0
4 years ago
What is the difference between the number of electrons in an atom of selenium,se, and the number of electrons in an atom of alum
Daniel [21]

Selenium has 36 electrons34(atomic number) + 2(amount of electrons gained in the <span>ion, has a 2- charge) = 36
</span>To identify the number of electrons an element has, all you need is a periodic table. Identify the atomic number (the smallest of the 2 numbers in the box). That number will be the number of protons which is also the number of electrons. 
*number Atoms of all elements are made up of three primary particles: protons, neutrons, and electrons. The "sub-atomic" particles each have specific properties that such as size, electrical charge, etc. that are crucial for the stability of the atom. The particles break down like this: Particle Relative size Charge Location How to determine

Proton 1 + in the nucleus # of protons= element's atomic # (use periodic table)

Electron 0 - outside nucleus # of electrons=# of protons(in neutral, "normal" atom)

Neutron 1 0 in the nucleus Must be told or given (ie. can vary--isotopes--

for small elements most common form often

consists of isotope where #protons=#neutrons) Aluminum has 13 electrons because it needs 13 negative charges to balance the 13 postively-charged protons (which is what the periodic table told us it contains). This will make the Aluminum atom electrically neutral. 
5 0
3 years ago
11. Consider the velocity vs time graph below. Which object is not moving at time = 0?
MAXImum [283]
I’m guessing it’s all of the above
8 0
3 years ago
Three guns are aimed at the center of a circle, and each fires a bullet simultaneously. The directions in which they fire are 12
ikadub [295]

Answer:

The unknown mass of the bullet is  m1=3.751x10^{-3} kg

Explanation:

According to Newton's laws of motion, when a net external force acts on a body of mass  <u><em>m</em></u> , it results in change in momentum of the body and is given by:

F=\frac{P}{dt}

Where:

P

is the linear momentum of the body

As a consequence, when there are no external forces acting on the body the total momentum remains conserved i.e.

Given:

m_{2}=5.79x10^{-3}kg  \\m_{3}=5.79x10^{-3}kg\\v_{2}=v_{3}=392 \frac{m}{s}\\

For momentum along the y-direction to be zero, it is achieved when the equal masses are moving at angles of  

θ1=180°, θ2=60°, θ3=-60°

Therefore, from conservation of momentum along x - direction:

m_{1}*v_{1}*cos(180)+m_{2}*v_{2}*cos(60)+m_{3}*v_{3}*cos(-60)=0\\m_{1}*605\frac{m}{s}*cos(180)+5.79x10^{-3}kg *392\frac{m}{s}*cos(60)+5.79x10^{-3}kg*392\frac{m}{s}*cos(-60)=0\\

-m_{1}*605+5.79x10^{-3}kg*196\frac{m}{s}+5.79x10^{-3}kg*196\frac{m}{s}=0\\m_{1}*605kg= 2.26968\frac{kg*m}{s}\\m_{1}=3.75 x10^{-3} kg

3 0
3 years ago
A roadway for stunt drivers is designed for racecars moving at a speed of 40 m/s. A curved section of the roadway is a circular
Fynjy0 [20]

Answer:

Bank angle = 35.34o

Explanation:

Since the road is frictionless,

Tan (bank angle) = V^2/r*g

Where V = speed of the racing car in m/s, r = radius of the arc in metres and g = acceleration due to gravity in m/s^2

Tan ( bank angle) = 40^2/(230*9.81)

Tan (bank angle) = 0.7091

Bank angle = tan inverse (0.7091)

Bank angle = 35.34o

3 0
3 years ago
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