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3 years ago

The amount of force needed to keep a 0.5 kg football moving at a constant speed of 8 m/s

Physics

1 answer:

Mice21 [21]3 years ago

3 0

Answer:

0 N

Explanation:

The football is moving at constant speed, so it's not accelerating.

∑F = ma

F = (0.5 kg) (0 m/s²)

F = 0 N

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A person of mass m will bungee-jump from a bridge over a river where the height from the bridge to the river is h. The bungee co

Likurg_2 [28]

Answer: $k_{min}=\frac{18mg}{h}$

Explanation:

Given

mass of person is m

Distance between bridge and river is h

chord has an un-stretched length of $\frac{2h}{3}$

Let spring constant be k

Person will just stop before hitting the river

Conserve energy i.e. Potential Energy of Person is converted in to elastic energy of chord

$mgh=\frac{kx^2}{2}$

$x=h-\frac{2h}{3}=\frac{h}{3}$

$mgh=\frac{kh^2}{18}$

$k=\frac{18mg}{h}$

Thus $k_{min}=\frac{18mg}{h}$

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3 years ago

Horace has invented a unique pair of reading glasses that have two small light bulbs at the bottom wired in series, so that he c

ElenaW [278]

Answer:

The current drawn by Horace’s reading glasses is 0.8 A.

Explanation:

Given that,

Resistance of each bulb, R = 2 ohms

Voltage of the system, V = 3.2 volts

These two bulbs are connected in series. The equivalent resistance will be 2 ohms +2 ohms = 4 ohms

Let I is the current drawn by Horace’s reading glasses. Using Ohm's law to find it such that :

$V=IR\\\\I=\dfrac{V}{R}\\\\I=\dfrac{3.2}{4}\\\\I=0.8\ A$

So, the current drawn by Horace’s reading glasses is 0.8 A.

3 0

3 years ago

Jake calculates that the frequency of a wave is 230 hertz, and its wave is moving at 460 m/s. What is the wavelength of the wave

Nesterboy [21]

Wavelength = (speed) / (frequency) = (460 m/s) / (230/sec) = <em>2 meters</em>

3 0

3 years ago

A car accelerates from 20mi/hr to 60mi/hr. How many times greater is the car's kinetic energy at the higher speed compared to th

Ainat [17]

Answer:

9 times

Explanation:

Kinetic energy is:

KE = ½ mv²

When we triple the velocity, the kinetic energy increases by a factor of 9.

9KE = ½ m(3v)²

4 0

2 years ago

What is the change in length of a 1400. m steel, (12x10^-6)/(C0) , pipe for a temperature change of 250.0 degrees Celsius? Remem

8090 [49]

Answer:

$\Delta L = 4.2 m$

Explanation:

As per the formula of thermal expansion we know that

$L = L_o(1 + \alpha\Delta T)$

so here we will have

$L_o = 1400 m$

$\alpha = 12 \times 10^{-6} per ^oC$

$\Delta T = 250 degree C$

so here change in the length of the rod is given as

$\Delta L = L - L_o$

$\Delta L = L_o \alpha \Delta T$

$\Delta L = 1400 (12 \times 10^{-6})(250)$

$\Delta L = 4.2 m$

8 0

3 years ago