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3 years ago

When is the total momentum of a system conserved?

Physics

1 answer:

valentina_108 [34]3 years ago

5 0

Answer:

When the net external force is zero

Explanation:

We can answer to this question by referring to Newton's Second Law, which can be written in the following form

$F=\frac{\Delta p}{\Delta t}$

where

F is the net external force acting on a system

$\Delta p$ is the change in momentum of the system

$\Delta t$ is the time interval

When the total momentum of a system is conserved (so, it does not change), its variation is zero:

$\Delta p = 0$

In order to satisfy this condition, we see from the formula that we must also have

F = 0

so the net external force acting on the system must be zero.

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If all of the forces acting on an object are balanced, then:

kondaur [170]

A. the direction the object is moving in will not change.

B. the acceleration of the object will be 0 m/s2

Explanation:

We can answer this problem by using Newton's second law of motion:

$\sum F = ma$

where

$\sum F$ is the net force acting on an object

m is the mass of the object

a is its acceleration

In this problem, all the forces acting on the object are balanced, therefore the net force is zero:

$\sum F=0$

which means that also the acceleration is zero:

$a=0$

Acceleration is equal to the rate of change of velocity: therefore, zero acceleration means that the velocity of the object does not change. We can now analyze the given statements:

A. the direction the object is moving in will not change. --> TRUE, because the velocity is not changing.

B. the acceleration of the object will be 0 m/s2 --> TRUE, as we stated above

c. the object will not be in motion. --> FALSE: we just know that its velocity is constant, but it can be different from zero

D. the velocity of the object will be 0 m/s. --> FALSE, for the same reason stated in C

Learn more about Newton's second law of motion:

brainly.com/question/3820012

#LearnwithBrainly

3 0

3 years ago

A car is 200 m from a stop sign and traveling toward the sign at 40.0 m/s. At this time, the driver suddenly realizes that she m

Zinaida [17]

Answer:

4.17 m/s²

Explanation:

We are told the reaction time is 0.2 s. Now, during this reaction time the car is going to travel an additional distance of : x = u × t = 40 × 0.2 = 8 m

where u is the initial velocity of the car which is 40.0 m/s.

We are told that he had 200 m to stop before applying brakes. Thus, after applying brakes, he now has a distance to cover of; s = 200 - 8 = 192 m

Since vehicle is coming to rest acceleration would be negative, thus using Newton's equation of motion, we have;

v ² = u² - 2as

v = 0 m/s since it's coming to rest

u = 40 m/s

s = 192 m

Thus;

0² = 40² - 2(a)(192)

0² = 1600 - 384a

a = 1600/384

a = 4.17 m/s²

6 0

3 years ago

A child pulls a wagon at a constant velocity along a level sidewalk. The child does this by applying a 22 newton force to the wa

Jlenok [28]

Answer:

The answer is 18 N.

Explanation:

A force can be divided into components x and y components. The component along the x-axis is called the horizontal component and along the y-axis is called the vertical component. In this case, as the force is in a horizontal direction and is also known as x-component of force. The x- component of force is

Fx = Fcosθ

Fx = 22(cos 35°)

Fx = 22 x 0.819

Fx = 18 N

Child's horizontal pull forces are equal to that of frictional resistance force on the wagon.

5 0

3 years ago

1. A student is biking to school. She travels 0.7 km north, then realizes something has fallen out of her bag.

Snezhnost [94]

Explanation:

(a) Displacement of an object is the shortest path covered by it.

In this problem, a student is biking to school. She travels 0.7 km north, then realizes something has fallen out of her bag. She travels 0.3 km south to retrieve her item. She then travels 0.4 mi north to arrive at school.

0.4 miles = 0.64 km

displacement = 0.7-0.3+0.64 = 1.04 km

(b) Average velocity = total displacement/total time

t = 15 min = 0.25 hour

$v=\dfrac{1.04\ km}{0.25\ h}\\\\v=4.16\ km/h$

Hence, this is the required solution.

8 0

3 years ago

Describe the evolution of a pulsar over time, in particular how the rotation and pulse signal changes over time.

madam [21]

Answer:

As beams of particles and their associated energy are given off, the pulsar will lose energy slowly, which will decrease the rate of its rotation. The frequency of pulses would therefore decrease, so that fewer pulses are observed in a given time span. The strength of the pulse signal will also decrease so the pulses will become fainter. Eventually, the pulsar should rotate so slowly and have such a low emission of radiation that it would no longer be observable.

3 0

3 years ago