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3 years ago

A car increases its speed from 20km/hr to 50km/hr in seconds. Its acceleration is _____.

Physics

1 answer:

mash [69]3 years ago

7 0

Answer:

Option D

0.83 m/s2

Explanation:

Time is assumed as 10 seconds

First, convert the speeds from km/h to m/s

20 km/h\times \frac {1000 m}{3600 s}=5.555555556 m/s \approx 5.56 m/s

50 km/h\times \frac {1000 m}{3600 s}=13.88888889 m/s \approx 13.89 m/s

Acceleration, $a=\frac {v-u}{t}$ where u and v are the initial and final velocities respectively, t is the time taken to accelerate.

Substituting 13.89 m/s for v, 5.56 m/s for u and 10 s for t then

$a=\frac {13.89-5.56}{10}=0.8333333 m/s^{2}\approx 0.83 m/s^{2}$

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11. Hans and Frans are two workers being considered for a job at the UPS loading dock. Hans boasts that he can lift a 100 kg box

Marta_Voda [28]

Answer:

Hans is more powerful

Explanation:

Power: This can be defined as the rate at which work is done or energy is used up.

The expression for power is given as,

P = E/t

P = mgh/t................. Equation 1

Where P = power, W = Work, t = time, m = mass, h = height, g = acceleration due to gravity.

Hans' power

P = mgh/t

Given: m = 100 kg, h = 2 m, g = 9.8 m/s², t = 3 s

Substitute into equation 1

P = 100(9.8)(2)/3

P = 653.33 W.

Frans' power

P' = mgh/t

Given; m = 200 kg, h = 5 m, t = 20 s.

P' = 200(5)(9.8)/20

P' = 9800/20

P' = 490 W

from the above,

since P>P'

Hence, Hans is more powerful

8 0

3 years ago

A 56.0kg ice skater spins about a vertical axis through her body with her arms horizontally outstretched, making 2.50 turns each

Arada [10]

Answer:

Net force = 129.4, Force as multiple of weight of her hand = 18.84

Explanation:

Given Data:

Total body weight = 56.0 kg ;

no. of turns = 2.5/second ;

hand to hand distance = 1.5m ;

weight of hand = 1.25% of body weight ;

Solution:

mass of hand = $\frac{1.25}{100}$ *56 = 0.7kg ;

radius = d/2 = 1.5/2 = 0.75m ;

Now we need to find velocity, as we know that velocity can be calculated by dividing distance by time

v = d/t = $\frac{2.5*2*3.14*0.75}{1}$ = 11.775 m/s or 12 m/s;

The formula to calculate force is given as

F = mv²/r = (0.7*11.775²)/0.75 = 129.4 N

To calculate force as multiple of weight on her hand, we need to calculate the gravitational force W on her hand first.

W = gm = 9.81 * 0.7 = 6.867 N

Now the wieght on her hand can be represented by

$\frac{Force_{net} }{weight of hand}$ = 129.4 / 6.867 = 18.84

3 0

3 years ago

As the temperature of an object increases, the wavelength of the brightest light emitted _______

alexira [117]

Answer:

option (B) decreases

Explanation:

According to the Wein's displacement law, the minimum wavelength of the radiated emission is inversely proportional to the absolute temperature of the body which emits radiation.

$\lambda_{m}\alpha \frac{1}{T}$

Where, T is the absolute temperature of the body and λm is the minimum wavelength of heat radiated.

Here, as the temperature increases, the wavelength decreases.

4 0

3 years ago

Three +3.0-μC point charges are at the three corners of a square of side 0.50 m. The last corner is occupied by a −3.0-μC charge

kramer

Answer:

E = 440816.32 N/C

Explanation:

Given data:

Three point charge of charge equal to +3.0 micro coulomb

fourth point charge = - 3.0 micro coulomb

side of square = 0.50 m

$K =1/4 \pi \epsilon_0 = 8.99 \times 10^9$ N.m^2/c^2

Due to having equal charge on center of square, 2 charge produce equal electric field at center and other two also produce electric field at center of same value

So we have

$E_1 + E_3 = 0$