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2 years ago

8

When skydiver nellie opens her parachute, the air drag pushing the chute upward is stronger than earth's force of gravity pullin

g her downward. a friend says this means she should start moving upward?

1 answer:

Reil [10]2 years ago

5 0

No, the skydiver does not start moving upward. Yes, initially the air drag is stronger than the weight, and so there is a net force pushing upward, and the result of this force (because of F=ma) is a deceleration of the skydiver (because the force goes against the direction of motion). However, the air drag is proportional to $v^2$ , the square of the velocity. Thus, as the velocity of the skydiver decreases, so does the air drag, and eventually the air drag becomes smaller than the weight. So the skydiver continues his motion towards the ground.

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A bee wants to fly to a flower located due North of the hive on a windy day. The wind blows from East to West at speed 6.68 m/s.

Aleonysh [2.5K]

Answer: $53.31\°$ East of North

Explanation:

We have the following data:

Speed of the wind from East to West: $6.68 m/s$

Speed of the bee relative to the air: $8.33 m/s$

If we graph these speeds (which in fact are velocities because are vectors) in a vector diagram, we will have a right triangle in which the airspeed of the bee (its speed relative to te air) is the hypotense and the two sides of the triangle will be the <u>Speed of the wind from East to West</u> (in the horintal part) and the <u>speed due North relative to the ground</u> (in the vertical part).

Now, we need to find the direction the bee should fly directly to the flower (due North):

$sin \theta=\frac{Windspeed-from-East-to-West}{Speed-bee-relative-to-air}$

$sin \theta=\frac{6.68 m/s}{8.33 m/s}$

Clearing $\theta$ :

$\theta=sin^{-1} (\frac{6.68 m/s}{8.33 m/s})$

$\theta=53.31\°$

6 0

2 years ago

a pulley of radius 0.9m is used to lift a bucket from the well. if it took 3.6 rotations for the pulley to take water out of the

Alex777 [14]

Answer:

h = 20.36[m]

Explanation:

To solve this problem we must calculate the perimeter (length of a circumference) of the circumference, which is denoted by the following equation:

L = 2*π*r

where:

r = radius = 0.9[m]

π = 3.1416

L = 2*(3.1416)*(0.9)

L = 5.654[m]

Now we know that the pulley or circumference had to rotate 3.6 times to get the water out of the well. In this way the depth of the well can be calculated by means of the following equation:

h = 3.6*L

h = 3.6*5.654

h = 20.36[m]

6 0

2 years ago

Carts A and B are identical and are moving toward each other on a track. The speed of cart A is v, while the speed of cart B is

borishaifa [10]

Answer: k= $\frac{5mv^{2} }{2}$

Explanation:

Recall that the formula for kinetic energy is given below as

k = $\frac{mv^{2} }{2}$

where k=kinetic energy (joules), m= mass of object (kg), v= velocity of object m/s)

For cart A

$m_{a}$ = mass of cart A

$v_{a}$ = v = velocity of cart A

$K.E_{a}$ = kinetic energy of cart A

hence, $K.E_{a}$ = $\frac{m_{a}v^{2} }{2}$

For cart B

$m_{b}$ = mass of cart B

$v_{b}$ = 2v = velocity of cart B

$K.E_{b}$ = kinetic energy of cart B

hence, $K.E_{b}$ = $\frac{m_{b}(2v^{2}) }{2}$ = 2 $m_{b} v^{2}$

from the question, both cart are identical which implies they have the same mass i.e $m_{a}$ = $m_{b}$ = m which implies that

$K.E_{a}= \frac{mv^{2} }{2}$ and $K.E_{b} =2mv^{2}$

The total kinetic energy K is the sum of cart A and cart B kinetic energy

$K=K.E_{a} + K.E_{b}$

$K=\frac{mv^{2} }{2} + 2mv^{2}$

hence

$K=\frac{5mv^{2} }{2}$

6 0

2 years ago

Sophia is planning on going down an 8-m water slide. Her weight is 50 N. She knows that she has gravitational potential energy (

Pepsi [2]

Answer:The higher up an object is the greater its gravitational potential energy. The larger the distance something falls through the greater the amount of GPE the object loses as it falls. As most of this GPE gets changed into kinetic energy, the higher up the object starts from the faster it will be falling when it hits the ground. So a change in gravitational potential energy depends on the height an object moves through.

Explanation: Lifting an apple up 1 metre is easier work than lifting an apple tree the same height. This is because a tree has more mass, so it needs to be given more gravitational potential energy to reach the same height.

6 0

2 years ago

This problem explores the behavior of charge on conductors. We take as an example a long conducting rod suspended by insulating

Olegator [25]

Answer:

rod end A is strongly attracted towards the balls

rod end B is weakly repelled by the ball as it is at a greater distance

Explanation:

When the ball with a negative charge approaches the A end of the neutral bar, the charge of the same sign will repel and as they move they move to the left end, leaving the rod with a positive charge at the A end and a negative charge of equal value at end B.

Therefore rod end A is strongly attracted towards the balls and

rod end B is weakly repelled by the ball as it is at a greater distance

3 0

2 years ago