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BaLLatris [955]
4 years ago
12

n a downhill ski race, surprisingly, little advantage is gained by getting a running start. (This is because the initial kinetic

energy is small compared with the gain in gravitational potential energy on even small hills.) To demonstrate this, find the final speed and the time taken for a skier who skies 70.0 m along a 30â slope neglecting friction: (a) Starting from rest. (b) Starting with an initial speed of 2.50 m/s. (c) Does the answer surprise you? Discuss why it is still advantageous to get a running start in very competitive events.
Physics
1 answer:
Annette [7]4 years ago
7 0

Answer:

Explanation:

a ) starting from rest , so u = o and initial kinetic energy = 0 .

Let mass of the skier = m

Kinetic energy gained = potential energy lost

= mgh = mg l sinθ

= m x 9.8 x 70 x sin 30

= 343 m

Total kinetic energy at the base = 343 m  + 0 = 343 m .

b )

In this case initial kinetic energy = 1/2 m v²

= .5 x m x 2.5²

= 3.125 m

Total kinetic energy at the base

= 3.125 m  + 343 m

= 346.125 m

c ) It is not surprising as energy gained due to gravitational force by the earth is enormous . So component of energy gained due to gravitational force far exceeds the initial kinetic energy . Still in a competitive event , the fractional initial kinetic energy may be the deciding factor .

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1.- An elevator is being lowered at a constant speed by a steel cable attached to an electric motor. Which statement is correct?
Nady [450]

Answer:

the correct one is C

Explanation:

For this exercise we must use the work definition

    W = F. s

Where the bold characters indicate vectors and the point is the scalar producer

    W = F s cos θ

Where θ is the angles between force and displacement.

Let us support this in our case. The cable creates an upward tension and with the elevator going down the angle between them is 180º so the work of the cable on the elevator is negative.

The evade has a downward force, its weight so the force goes down and the displacement goes down, as both are in the same direction the work is positive

When examining the statements the correct one is C

4 0
3 years ago
A resistor R and another resistor 2R are connected in a series across a battery. If heat is produced at a rate of 10W in R, then
alekssr [168]

Answer:

Option B

Solution:

As per the question:

Heat produced at the rate of 10 W  

The resistor R and 2R are in series.

Also, in series, same current, I' passes through each element in the circuit.

Therefore, current is constant in series.

Also,

Power,P' = I'^{2}R

When current, I' is constant, then

P' ∝ R

Thus

\frac{P'}{2R} = \frac{10}{R}

P' = 20 W

5 0
3 years ago
A rocket with a mass of 62,000 kg (including fuel) is burning fuel at the rate of 150 kg/s and the speed of the exhaust gases is
mezya [45]

Answer:

h≅ 58 m

Explanation:

GIVEN:

mass of rocket M= 62,000 kg

fuel consumption rate =  150 kg/s

velocity of exhaust gases v= 6000 m/s

Now thrust = rate of fuel consumption×velocity of exhaust gases

=6000 × 150 = 900000 N

now to need calculate time t = amount of fuel consumed÷ rate

= 744/150= 4.96 sec

applying newton's law

M×a= thrust - Mg

62000 a=900000- 62000×9.8

acceleration a= 4.71 m/s^2

its height after 744 kg of its total fuel load has been consumed

h= \frac{1}{2}at^2

h= \frac{1}{2}4.71\times4.96^2

h= 58.012 m

h≅ 58 m

4 0
3 years ago
The resistance of a wire is not dependent on
Komok [63]

d. Current

It is opposing

3 0
3 years ago
Write an essay convincing a non-active person that swimming is beneficial. Create a swim test. Please dont take from other sourc
strojnjashka [21]

A nonactive person should go swimming because swimming is a great exercise and when you are swimming the bones are more oiled up and they are more lubed and moveable. There are so many benefits that swimming help, for example, swimming helps keep your heart rate up but takes some of the impact stress off your body, it builds endurance, muscle strength and cardiovascular  fitness, it helps you maintain a healthy weight, and healthy heart and lungs, it also helps tones muscles and builds strength, and lastly it provides an all-over body workout, as nearly all of your muscles are used during swimming. Swimming is a way to relax peacefully, alleviate stress, improving coordination balanced and posture, it improves flexibility. Before going to swim make sure you warm up and stretch your muscles and joints, have plenty of fluid on hand and drink regularly. Swimming has become one of the most popular sports in Australia and the nation is surrounded by water and swimming which is one of the huge passions that people have created. Its one way to have fun, keep fit, stay healthy and make friends. Swimming is also a healthy activity that you can continue for a lifetime and it has a low-impact that had many physical and mental health benefits. Swimming has helped a lot of special need kids, it's also an exercise that doctors recommend a lot to all their patients if they got an injury or when they have to do some kind of special exercise


Swim Test:


1. Jump into the pool, submerge fully, return to the surface and immediately begin swimming without pushing off the wall.

2. Swim in a horizontal position on top of the water using a forward crawl or breaststroke. The swimmer's arms must achieve full extension on every stroke, and he or she must maintain one or both of the strokes for the full 25-yard swim. Pausing is only allowed when the swimmer is rotating or turning to breathe.

3. Exit the pool without assistance using either the wall or pool ladder.

4. do 4 laps in 3 minutes

3 0
4 years ago
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