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3 years ago

A little girl kicks a soccer ball. It goes 10 feet and comes back to her. How is this possible?

1 answer:

8 0

A classic puzzle...

She either kicked it at a wall exactly 10 foot in front of her, where the ball rebounded off the wall.

Or, she kicked the ball straight up, vertically, at a 90 degree angle, where due to the law of gravity, which states that anything that goes up must come down, when the soccer ball reaches exactly 10 feet, it falls back down.
(Note: This is nearly impossible to achieve -- exactly 10 feet.)

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If the mass of the block is 5 kg and the speed 7 m/s, what is the work done on the block?

Kamila [148]

Answer:

A block of mass M = 5 kg is resting on a rough horizontal surface for which the coefficient of friction is 0.2. When a force F = 40N is applied, the acceleration of the block will be then (g=10ms

2 ).

Mass of the block=5kg

Coeffecient of friction=0.2

external applied force, F=40N

The angle at which the force is applied=30degree

So the horizontal component of force=Fcos30=40×

23 =20 3 N

While the uertical component of the force acting in upward direction=Fsin30=40× 21

=20N

The normal reaction from the surface (N)=mg−Fsin30=50−20=30N

So the ualue of limiting friction=μN=0.2×30=6N

Hence the net horizontal force on the block=Fcos30=μN=20

N−6N=28.64N

The horizontal acceleration of the block=

Fcos30−μN = 528.64

=5.73m/s 2

8 0

3 years ago

80 grams of iron at 100°C is dropped into 200 of water at 20°C contained in an iron vessel of mass 50 gram find the resulting te

vodka [1.7K]

Answer:

the resulting temperature is 23.37 ⁰C

Explanation:

Given;

mass of the iron, m₁ = 80 g = 0.08 kg

mass of the water, m₂ = 200 g = 0.2 kg

mass of the iron vessel, m₃ = 50 g = 0.05 kg

initial temperature of the iron, t₁ = 100 ⁰C

initial temperature of the water, t₂ = 20 ⁰C

specific heat capacity of iron, c₁ = 462 J/kg⁰C

specific heat capacity of water, c₂ = 4,200 J/kg⁰C

let the temperature of the resulting mixture = T

Apply the principle of conservation of energy;

heat lost by the hot iron = heat gained by the water

$m_1c_1 \Delta t_1 = m_2c_2\Delta t_2\\\\m_1c_1 (100 - T) = m_2c_2 (T- 20)\\\\0.08 \times 462 (100-T) = 0.2 \times 4,200 (T-20)\\\\36.96 (100-T) = 840 (T-20) \\\\100 - T = 22.72 (T-20)\\\\100-T = 22.72 T - 454.4 \\\\554.4 = 23.72T\\\\T = \frac{554.4}{23.72} \\\\T = 23.37 \ ^0C$

Therefore, the resulting temperature is 23.37 ⁰C

6 0

3 years ago

What is the easiest way to increase the magnetic force acting on the rotor in an induction motor?

Schach [20]

Answer:

Explanation:

Magnets are of two major forms namely the permanent magnet and the temporary magnets. Temporary magnets magnetizes and demagnetize easily while permanent magnets does not magnetizes and demagnetize easily.

This permanents magnets are applicable in loudspeakers, generators, induction motor etc.

To increase the

The following will tend to increase the magnetic force acting on the rotor in an induction motor.

1. Increasing the strength of the bar magnet. Increase in strength of the magnet will lead to increase in the magnetic force acting on the rotor.

2. Increase in the magnetic line of force also known as the magnetic flux around the magnet will also increase the magnetic force acting on the rotor.

6 0

3 years ago

Total charge is uniformly distributed on a spherical surface of radius R. The sphere is centered at the origin and spins around

Flauer [41]

Answer:

Explanation:

i have a A in physics

5 0

3 years ago

If the force is 4 newtons between two charged spheres separated by 3 centimeters, calculate the force between the same spheres s

il63 [147K]

Answer:

1 Newton

Explanation:

F=9*10^9*q0q1/r^2]]

F=9*10^9*(q0q1)/ r^2

r=3cm

F=4N

F=9*10^9*(q0q1)/3^2

4=9*10^9*(q0q1)/9

4=10^9 q0q1

q0q1=4/10^9

q0q1=4*10^-9

To calculate the force between the forces at a distance of 6 cm

F=9*10^9*(q0q1)/ r^2

=9*10^9*(4*10^-9)/6^2

=9*10^9*(4*10^-9)/36

=10^9*4*10^-9/4

=10^9*10^-9

=1 Newton

7 0

3 years ago