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4 years ago

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M A hockey player is standing on his skates on a froze pond when an opposing player, moving with a uniforn speed of 12 m/s, skat

es by with the puck. Aer 3.0s, the first player makes up his mind to chase his opponent. I he accelerates uniformly at 4.0 m/s, (a) how lon does it take him to catch his opponent, and (b) howhas he traveled in that time? (Assume the player wi the puck remains in motion at constant speed.)

1 answer:

Anni [7]4 years ago

8 0

<span>A car with a mass of 1500kg starts from rest and accelerates to a speed of 18m/s in 12s. Assume that the force of resistance remains contant at 400N during</span>

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5. {Chapter 6 Suppose you are traveling down the road in your car at highway speeds on a nice

Hitman42 [59]

Answer:

a) The 2 forces are equal

b) The impulse is the same

c) The change in momentum is the same

d) Inelastic

Explanation:

a)

According to Newton's third law of motion:

"When an object A exerts a force on an object B (action force), then object B exerts an equal and opposite force on object A (reaction force)"

In this problem, we can identify:

- The car as object A

- The bug as object B

Therefore:

- The force exerted by the car on the bug is the action force

- The force exerted by the bug on the car is the reaction force

According to Newton's third law of motion, these two forces are equal in magnitude, and opposite in direction.

b)

The impulse exerted on an object is equal to the product between the force exerted on it and the time taken:

$I=F\Delta t$

where

I is the impulse

F is the force exerted

$\Delta t$ is the time during which the force is applied

In this problem:

- The force F exerted on both the car and the bug is the same (according to what we said in part a)

- The time interval $\Delta t$ is the same for the two objects

Therefore, the impulse exerted on the bug is the same as the impulse on the car.

c)

The change in momentum of an object is defined as:

$\Delta p = m \Delta v$ (1)

where

m is the mass of the object

$\Delta v$ is the change in velocity of the object

However, according to the impulse theorem, the change in momentum of an object is also equal to the impulse it has experienced:

$\Delta p = I$

Therefore, since the impulse experienced by the bug and the car is the same (part b), this means that the change in momentum of the bug and the car is the same (and so by looking at eq.(1), we can conclude that the bug will experience a larger change in velocity, since its mass is smaller than that of the car).

d)

There are two types of collision:

Elastic collision: in an elastic collision, both the total momentum and the total kinetic energy of the system are conserved
Inelastic collision: in an inelastic collision, only the total momentum is conserved, while the total kinetic energy is not (part of the energy is converted into thermal energy due to the presence of friction forces)

In particular, inelastic collision occurs when the two objects stick together after the collision.

In this situation, we see that the bug and the car stick together after the collision: this means that the total kinetic energy of the system is not conserved, and therefore, this is an example of inelastic collision.

5 0

3 years ago

The frequency of the faintest audible sound is about 1,000Hz. What is the pressure variation corresponding to this sound.

astra-53 [7]

Answer:

Option B

$3\times 10^{-5}$

Explanation:

Variation of pressure, $\triangle P$ is given by

$\triangle P=\sqrt {2\rho vi}$

Where v is the speed of sound, i is the intensity, rho is the density of air whose value is taken as 1.2 Kg/m3

Taking the speed of sound in air as 334 m/s then

$\triangle P=\sqrt{2\times 1.2\times 334\times 1\times 10^{-12}}=2.831\times 10^{-5}\approx 3\times 10^{-5}$

3 0

3 years ago

Water that soaks into Earth may become _____ under the surface.

larisa [96]

If it soaks into the earths surface it becomes ground water

5 0

3 years ago

What is the measurement of six centimeters equal to?

AlladinOne [14]

Six centimeters equal to about two inches

8 0

3 years ago

During her high bar routine from question 2, Gabby Douglas slipped and falls from the high bar, landing on a 10 cm thick gymnast

tankabanditka [31]

a) 122.5 J

b) -122.5 J

c) -1884.6 N

d) -3769.2 N

e) $-753.8 m/s^2$

f) $a=-76.9 g$

Explanation:

a)

The kinetic energy of an object is the energy possessed by the object due to its motion.

Mathematically, it is given by:

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

where

m is the mass of the object

v is the speed of the object

Here, we want to find the kinetic energy of the head just before hitting the mat.

At that instant, the speed is:

v = 7 m/s

The mass of the head is:

m = 5 kg

So, the kinetic energy is

$K=\frac{1}{2}(5)(7)^2=122.5 J$

b)

According to the work-energy theorem, the work done by a force on an object is equal to the change in kinetic energy of the object:

$W=K_f - K_i$

where

W is the work done

$K_f$ is the final kinetic energy

$K_i$ is the initial kinetic energy

In this problem:

$K_i=122.5 J$ is the kinetic energy of the head just before hitting the mat

$K_f=0 J$ is the final kinetic energy (since the head comes to a stop)

So, the work done by the mat is:

$W=0-122.5 = -122.5 J$

The work is negative because the force exerted by the mat is opposite to the direction of motion of the head.

c)

The work exerted by a force on an object is given by

$W=Fd$

where

F is the force applied

d is the displacement of the object

W is the work done

In this problem:

W = -122.5 J is the work done by the mat on the head

d = 6.5 cm = 0.065 m is the displacement of the head (since it deflects the mat by this amount)

So, the average force exerted by the mat on the head is:

$F=\frac{W}{d}=\frac{-122.5}{0.065}=-1884.6 N$

(the negative sign indicates that the force is in direction opposite to the motion of the head)

d)

The force calculated in part d) represents the average force exerted by the mat on the head:

$F_{avg}=-1884.6 N$

We can assume that as the head first hits the mat, the initial force is zero, then increases at a constant rate up to a peak value of $F_{peak}$ , then it decreases again until the head stops.

In this case, the relationship between average force and peak force is:

$F_{avg}=\frac{0+F_{peak}}{2}$

And therefore, the peak impact force exerted by the mat on the head is:

$F_{peak}=2F_{avg}=2(1884.6)=-3769.2 N$

e)

The peak acceleration of the head can be found by using Newton's second law, which states that:

$F=ma$

where

F is the force on the head

m is the mass of the head

a is the acceleration

Here we have:

F = -3769.2 N is the peak force

m = 5 kg is the mass of the head

So, solving for the acceleration, we find:

$a=\frac{F}{m}=\frac{-3769.2}{5}=-753.8 m/s^2$

f)

The value of the acceleration due to gravity is

$g=9.8 m/s^2$

Here we want to express the peak acceleration of the head in terms of the acceleration due to gravity; so we can write:

$a=Ng$

where

$a=-753.8 m/s^2$ is the peak acceleration

N is the ratio between the peak acceleration and the gravity acceleration

Solving for N,

$N=\frac{a}{g}=\frac{-753.8}{9.8}=-76.9$

This means that the peak acceleration can be written as

$a=-76.9 g$

6 0

3 years ago