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3 years ago

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17. What speed must you toss a ball straight up so it takes 4 s to return to you? Be sure to show all work to support your answe

r.

1 answer:

Darya [45]3 years ago

3 0

If we tossed up a coin with some velocity then its acceleration in the air is due to gravity which we can take as a = - 9.8 m/s^2

Also it is given that coin returns to initial position after 4 s

So after 4 s its displacement will become ZERO

now in this process we can say that in whole motion of the coin the net displacement of coin is zero and its acceleration is due to gravity remains constant.

We can use kinematics here

$\Delta y = v_i t + \frac{1}{2} at^2$

$0 = v_i (4) - \frac{1}{2}(9.8)(4)^2$

$v_i = 19.6 m/s$

so approximate speed of the coin must be nearly 20 m/s

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What is the speed of a bobsled whose distance-time graph indicates that it traveled 119m in 29s?

Assoli18 [71]

Do 112m /29s which it will be 3.862 which if you round it, it will be 3.86 m/s

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3 years ago

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A car drives 23m/s east for 35 seconds. What is the displacement?

Lina20 [59]

Answer:

805m

Explanation:

Speed = displacement/time

Speed = 23m/s

Time = 35s

Displacement = speed × time

= 23 × 35

= 805m

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3 years ago

If a car is accelerating downhill under a net force 3674 N , what additional force would cause the car to have a constant veloci

Semenov [28]

Answer:

For the car to move with constant velocity the additional force required is $F__{dg} }= -3674 \ N$

Explanation:

From the question we are told that

The net force of the car is $F_{net} = 3674 \ N$

Generally the total force acting on the car is the net force plus the force due to gravity acting in direction of the car (Let denote it as $F__{dg}$ )

So the total force acting on the car is mathematically represented as

$F_{net} + F__{dg}} = F$

Here this F representing the total force can be mathematically represented as

$F = ma$

Now for constant velocity to be attained, the acceleration of the car will be zero

So at constant velocity

$F = m * 0$

=> $F = 0 \ N$

So

$F_{net} + F__{dg}} = 0$

=> $F__{dg} }= -F_{net}$

=> $F__{dg} }= -3674 \ N$

6 0

2 years ago

Which of the following materials is able to absorb large amounts of energy without changing temperature very much? air concrete

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3 years ago

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2. How far will a bird have traveled in 13 seconds if it maintained a speed of 31 m/s?

Flura [38]

#2

speed of bird = 31 m/s

time = 13 s

since here bird maintains its speed to be constant

so here the distance traveled is given by

$d = v*t$

$d = 31 * 13$

$d = 403 m$

so bird will travel 403 m distance while maintaining its speed to be constant

#3

average speed is the ratio of total distance covered and total time

here Ian walk 2 km then 0.5 km and then 2.5 km so the total distance is given as

$d = d_1 + d_2 + d_3$

$d = 2 + 0.5 + 2.5$

$d = 5 km$

total time of his full motion is

$t = 3 hours$

so the average speed of the motion is

$v = \frac{d}{t}$

$v = \frac{5}{3} = 1.67 km/h$

so here average speed of Ian is 1.67 km/h

#4

Initial speed of the truck is 6 m/s

after 4 s interval of time

final speed of the truck is 14 m/s

so the acceleration is rate of change in velocity

so it is given as

$a = \frac{v_f - v_i}{t}$

$a = \frac{14 - 6}{4}$

$a = 2 m/s^2$

so here truck accelerated with 2 m/s^2

#5

Here car starts from rest so its initial speed is 0

after 2.5 s interval of time

final speed of the car is 15 m/s

so the acceleration is rate of change in velocity

so it is given as

$a = \frac{v_f - v_i}{t}$

$a = \frac{15 - 0}{2.5}$

$a = 6 m/s^2$

so here car accelerated with 6 m/s^2

#6

a bag full of trash is dropped from the balcony

Here we can say when bag is in air

the net force on the bag is only due to its weight

so here we can use Newton's II law to find the acceleration of bag

$F = ma$

$mg = ma$

$a = g = 9.8 m/s^2$

so here bag will have constant acceleration during its whole motion as we can see that there is no change in the force and hence its acceleration always remains constant

3 0

3 years ago