An 81 kg stuntman jumps from the top of a building 29 m above a catching net. Assuming that air resistance exerts a 100 N force on the stuntman as he falls, determine his velocity just before he hits the net

Answers

Answer 1

Answer: In order to solve this, we can get all tangled up in acceleration,
or we can just add up the energy budget.

-- Gravitational potential energy = (mass) (grav accel) (height above something)

-- 29 m above the net, his potential energy is (81 x 9.8 x 29) = 23,020 joules

-- All the way down, air resistance exerts 100 N of force against him.
The energy burned up by air resistance is the work done = 100 x 29 = 2,900 joules.

-- The energy he has left when he hits the net is (23,020 - 2,900) = 20,120 joules.

-- When he hits the net, all of his energy is kinetic energy . . . (1/2) (m) (v²)

(1/2) (m) (v²) = 20,120

(40.5) (v²) = 20,120

v² = 20,120 / 40.5

v = square root of (20,120 / 40.5) = 22.3 meters per second (about 50 mph)

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When looking at human motives the following theorist developed a hierarchy of five needs that range from basic physiological needs to groeth or meta-needs
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In a closed system, a cart with a mass of 1.5 kg is rolling to the right at 1.4 m/s, while another cart of mass 1.0 kg is rolling to the left at the same speed. What is the total momentum of the system of two carts?a. 0.0 kgm/s b. 0.50 kgm/s c. 0.70 kgm/s d. 3.5 kgm/s

how are the direction of an object's acceleration and the direction of the same object's change in velocity related

Answers

The question is a lot like asking "How is your age related to
how long you have lived ?"

Those directions must be the same, because "acceleration"
means "change in velocity".

Choose the correct statement. A. Turning the steering wheel rotates the pinion and moves the rack up and down
B. The teeth on both the pinion and the rack are helical gears
C. A large pinion means the number of turns of the steering wheel is increased
D. The steering ratio is the same on all vehicles

Answers

The answer would be C

What is radiation? Transfer of heat through objects touching the source. Transfer of heat through direct physical contact. Transfer of heat through electromagnetic waves. Transfer of heat through the movement of particles.

Answers

Answer:

Transfer of heat through electromagnetic waves

Answer:

Transfer of heat through electromagnetic waves.

I got it right in a test

A water skier has a mass of 79.0 kg and accelerates at 1.40 m/s2. What is the net force acting on him? F = ___ NAnswer choices
56.4
111
77.6
0.018
80.4
774.2

Answers

The answer is 111.

Using Newton's Second Law, F=ma, plugging known values in we get:

F = (79kg)(1.4m/s^2) = 110.6N ≈ 111N

Final answer:

The net force acting on the water skier, calculated using Newton's second law (F=ma), is approximately 111 Newtons.

Explanation:

The net force acting on the water skier can be calculated using Newton's second law, which states that force equals mass times acceleration (F=ma). In this instance, the skier's mass (m) is 79.0 kg and his acceleration (a) is 1.40 m/s2.

By multiplying these values together (F = 79.0 kg * 1.40 m/s2), we find that the net force acting on him is 110.6 Newtons (N). However, this exact value is not listed in the answer choices. Among the given choices, 111 N would be the closest approximation to the calculated value.

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The source of the centripetal force that arises when a runner rounds a curve on a track is _____.tension
friction
weight
gravity

Answers

while taking a turn on a track, the track provides the frictional force acting towards the center of the curve. we know that to move in a curve, centripetal force is required. here since the frictional force acts towards the center, it provides the necessary centripetal force to move in circle. hence the correct choice is

friction

It's actually Friction.

I just did the test and got it right.

If a train is 100 km away, how much sooner would you hear the train coming by listening to the rails (iron) as opposed to listening for it standing by the track? In other words, how much faster will the sound travel through the iron rails than through the air? Assume the air temperature is 0°C.Sound will reach you ______ seconds sooner.

302

324

280

Answers

Wellll . . . it's doubtful that you'd hear the sound of a train
from 100 km away (about 62 miles), but this is a fun problem
so let's go through it just for the math.

Online, I looked up the speed of sound in various materials.
Here's what I found:

-- Speed of sound in normal air . . . . . 343 m/s

-- Speed of sound in iron . . . . . 5,130 m/s

But let's go a little farther !
Rails used to be made of cast iron or wrought iron.
But now they're made of hot rolled steel.

-- Speed of sound in steel . . . . . 6,100 m/s

   Time to cover the distance = (distance) / (speed)

   Time through air = (100,000 m) / (343 m/s)

   = 291.5 sec = 4 minutes 51.5 seconds

Time through old iron rails = (100,000 m) / (5,130 m/s)

   =   19.5 seconds (272 sec sooner)

Time through new steel rails = (100,000 m) / (6,100 m/s)

   = 16.4 seconds   (275 sec sooner)

Final answer:

The speed of sound varies in different mediums. In Physics, the speed of sound in air at 0°C is about 331.5 m/s, while in iron it's about 5130 m/s. If a train is 100 km away, the sound travelling through the iron rails would reach you approximately 282 seconds sooner than the sound through the air.

Explanation:

In Physics, the speed at which sound travels depends on the medium through which it's travelling. The speed of sound in air at 0°C is approximately 331.5 m/s. On the other hand, the speed of sound in iron is about 5130 m/s.

To determine how much sooner you would hear the train, we need to calculate the difference in time it takes for the sound to travel through these two mediums.

When the train is 100 km away, we get the following:

Time through air: 100000 m / 331.5 m/s = 301.66 seconds
Time through iron: 100000 m / 5130 m/s = 19.49 seconds

The difference is, therefore, approximately: 301.66 - 19.49 = 282.17 seconds. Thus, the sound will reach you 282 seconds sooner if you listen to the rails rather than the air.

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