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3 years ago

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A child standing on a bus remains still when the bus is at rest. When the bus moves forward and then slows down, the child conti

nues moving forward at the original speed. This is an example of

2 answers:

expeople1 [14]3 years ago

3 0

Newton's first law of motion

dlinn [17]3 years ago

3 0

The best answer would be, <u><em>Newton's first law of motion. </em></u>

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Calculate the work done if a boy lifts a bag of cement 500N to the floor of a lorry 2.5m above the ground

eduard

Answer:

W = 1250 J = 1.25 KJ

Explanation:

The work done by the boy is due to the change in the position of the cement vertically. Hence, the work done in this case will be equal to the potential energy of the cement:

$W = P.E\\W = mgh$

where,

W = Work done = ?

mg = W = weight of cement = 500 N

h = height covered = 2.5 m

Therefore,

$W = (500\ N)(2.5\ m)$

<u>W = 1250 J = 1.25 KJ</u>

4 0

2 years ago

A mother and daughter press their hands together and then push apart while ice skating. Immediately after they push away from ea

kherson [118]

Answer:

J

Explanation:

The daughter moves with greater acceleration backwards because of her weight.

7 0

3 years ago

Read 2 more answers

A group of students performed a compression experiment where they placed weights on top of a cylinder of material and measured t

kolbaska11 [484]

The material that the cylinder is made from is Butyl Rubber.

<h3>What is Young's modulus?</h3>

Young's modulus, or the modulus of elasticity in tension or compression, is a mechanical property that measures the tensile or compressive strength of a solid material when a force is applied to it.

<h3>Area of the cylinder</h3>

A = πr²

$A = \pi \times (0.02)^2 = 0.00126 \ m^2$

<h3>Young's modulus of the cylinder</h3>

$E = \frac{stress}{strain} \\\\E = \frac{F/A}{e/l} \\\\E = \frac{Fl}{Ae} \\\\$

Where;

e is extension

When 5 kg mass is applied, the extension = 10 cm - 9.61 cm = 0.39 cm = 0.0039 m.

$E = \frac{(5\times 9.8) \times 0.1}{0.00126 \times 0.0039} \\\\E = 9.97 \times 10^5 \ N/m^2\\\\E = 0.000997 \times 10^9 \ N/m^2\\\\E = 0.000997 \ GPa\\\\E \approx 0.001 \ GPa$

When the mass is 50 kg,

extension = 10 cm - 7.73 cm = 2.27 cm = 0.0227 m

$E = \frac{(50\times 9.8) \times 0.1}{0.00126 \times 0.0227} \\\\E = 1.7 \times 10^6 \ N/m^2\\\\E = 0.0017 \times 10^9 \ N/m^2\\\\E = 0.0017 \ GPa\\\\E \approx 0.002 \ GPa$

The Young's modulus is between 0.001 GPa to 0.002 GPa

Thus, the material that the cylinder is made from is Butyl Rubber.

Learn more about Young's modulus here: brainly.com/question/6864866

3 0

3 years ago

Read 2 more answers

The electron gun in a television tube is used to accelerate electrons with mass 9.109 × 10−31 kg from rest to 3 × 107 m/s within

zaharov [31]

Answer:

Electric field, E = 40608.75 N/C

Explanation:

It is given that,

Mass of electrons, $m=9.1\times 10^{-31}\ kg$

Initial speed of electron, u = 0

Final speed of electrons, $v=3\times 10^7\ m/s$

Distance traveled, s = 6.3 cm = 0.063 m

Firstly, we will find the acceleration of the electron using third equation of motion as :

$a=\dfrac{v^2-u^2}{2s}$

$a=\dfrac{(3\times 10^7)^2}{2\times 0.063}$

$a=7.14\times 10^{15}\ m/s^2$

Now we will find the electric field required in the tube as :

$ma=qE$

$E=\dfrac{ma}{q}$

$E=\dfrac{9.1\times 10^{-31}\times 7.14\times 10^{15}}{1.6\times 10^{-19}}$

E = 40608.75 N/C

So, the electric field required in the tube is 40608.75 N/C. Hence, this is the required solution.

3 0

3 years ago

An ideal transformer has 75 turns in the primary coil and n turns in the secondary coil. a 120 v rms 60hz ac voltage source is c

denpristay [2]

think you messed up the symbol for resistor as resistors are measured in ohms where the symbol used for ohms is Greek omega

solving for average power in secondary coil:

average power =(current rms)^2*resistance⇒with a little algebra:

current rms=(√average power/resistance)

current rms=√160W/10Ω

current rms=4amps.

average power is also equal to current rms*voltage rms

with some algebra we can solve for voltage in the secondary wire:

voltage rms= average power/ current rms

voltage rms= 160W/4A

voltage rms=40Volts

now that we have voltage in the soecondary we can solve for the amount of turns in the secondary: Voltage secondary/voltage primary=number of turns in secondary/ number of turns in primary. using some algerbra we can solve for number of turns in secondary: (Voltage secondary/voltage primary)*number of turns in primary=number of turns in secondary

(40V/120V)*75turns=number of turns in secondary

number of turns in secondary=25turns

4 0

3 years ago