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3 years ago

Mary has a mass of 40 kg and sprints at 1 m/s. How much kinetic energy does she have?

Physics

1 answer:

Sav [38]3 years ago

8 0

Answer:

20 J

Explanation:

Kinetic energy is given as half of the product of mass and the square of velocity of an object:

KE = $\frac{1}{2}mv^2$

where m = mass = 40 kg

v = velocity = 1 m/s

Hence, Mary's kinetic energy is:

KE = $\frac{1}{2} * 40 * 1^2$

KE = 20 * 1 = 20 J

She has a kinetic energy of 20 J.

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A machinist with normal vision has a near point at 25 cm. The machinist wears eyeglasses in order to do close work. The power of

Alik [6]

Answer:

17.4 cm

Explanation:

Power of lens = +1.75 diopters

Focal length of lens

$f=\frac{100}{1.75}=\frac{400}{7}$

This is a convex lens as focal the diopter given is positive which makes the focal length positive. Image distance will be negative.

v = -25

$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}\\\Rightarrow \frac{1}{-25}-\frac{1}{u}=\frac{1}{\frac{400}{7}}\\\Rightarrow -\frac{1}{u}=\frac{7}{400}+\frac{1}{25}\\\Rightarrow \frac{1}{u}=-\frac{7}{400}-\frac{1}{25}\\\Rightarrow \frac{1}{u}=-0.0575\\\Rightarrow u=-17.4\ cm$

∴ The new near point is 17.4 cm

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3 years ago

Explain how airplane wings and the wings of birds affect the air flowing over them to produce lift

d1i1m1o1n [39]

Because the air in their wings helps them fly

6 0

3 years ago

an 1150kg elevator moving down speeds up at a rate of 3.5m/s. what is the tension in the supporting cables?

gtnhenbr [62]

Answer:

The tension force in the supporting cables is 7245N

Explanation:

There are two forces acting on the elevator: the force of gravity pointing down (+) with magnitude (elevator mass) x (gravitational acceleration), and the tension force of the cable pointing up (-) with an unknown magnitude F. The net force is the sum of these forces:

$F_{net} = F_g - F = m\cdot g - F\\$

We are given the resulting acceleration along with the mass, i.e., we know the net force, allowing us to solve for F:

$1150kg\cdot 3.5\frac{m}{s^2}= 1150kg \cdot 9.8\frac{m}{s^2}-F\\\implies F = 1150kg\cdot(9.8-3.5)\frac{m}{s^2}= 7245N$

The tension force F in the supporting cables is 7245N

3 0

3 years ago

Mains electricity is an ac supply. Explain the difference between direct and alternating potential difference.

Gennadij [26K]

Direct current (DC) is the flow of electric charge in only one direction. It is the steady state of a constant-voltage circuit. Most well-known applications, however, use a time-varying voltage source. Alternating current (AC) is the flow of electric charge that periodically reverses direction.

<h2>#LETS STUDY</h2>

5 0

3 years ago

Ezekiel pushes a 34 kg sled with 101 N for 8.0 m. How much work did he do on the sled?

Simora [160]

Answer: 810 J

Explanation: work W = F·s = 101 N · 8.0 m = 808 J

Force F = u mg = 101 N in which u is friction constant. Also mass is included in force.

7 0

2 years ago