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3 years ago

An object at rest does not ___ and an object in motion does not _, unless an ___ force acts upon it

Physics

1 answer:

mel-nik [20]3 years ago

5 0

Answer:

An object at rest does not move and an object in motion does not change its velocity, unless an external force acts upon it

Explanation:

This statement is also known as Newton's first law, or law of inertia.

It states that the state of motion of an object can be changed only if there is an external force (different from zero) acting on it: therefore

- If an object is at rest, it will remain at rest if there is no force acting on it

- If an object is moving, it will continue moving at constant velocity if there is no force acting on it

This phenomenon can be also understood by looking at Newton's second law:

F = ma

where

F is the net force on an object

m is the mass

a is the acceleration

If the net force is zero, F = 0, the acceleration of the object is also zero, a = 0: therefore, the velocity of the object does not change, and it will continue moving at the same velocity (which can be zero, if the object was at rest).

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A falling stone is at a certain instant 90 feet above the ground. two seconds later it is only 10 feet above the ground. if it w

choli [55]

The equation relevant to this is:

S(t) = So + Vot - At²/2

Therefore we can create two equations:
S(t) = 90 = So - 4t - 16.1t² --> eqtn 1
S(t+2) = 10 = So - 4(t+2) - 16.1(t+2)² --> eqtn 2

Expanding eqtn 2:
10 = So - 4t - 8 - 16.1(t² + 4t + 4)
10 = So - 4t - 8 - 16.1t² - 64.4t - 64.4
10 + 8 + 64.4 = So - 68.4t - 16.1t²
82.4 = So - 68.4t - 16.1t² --> eqtn 3

Subtracting eqtn 1 by eqtn 3:

90 = So - 4t - 16.1t²

82.4 = So - 68.4t - 16.1t²

=> 7.6 = 64.4t

t = 0.118 s

Therefore calculating for initial height So:

82.4 = So - 68.4(0.118) - 16.1(0.118)²

So = 90.7 ft

7 0

3 years ago

You pull with a force of 295 N on a rope that is attached to a block of mass 22 kg, and the block slides across the floor at a c

Sergeeva-Olga [200]

Answer:

Fnet = 0

Explanation:

Since the block slides across the floor at constant speed, this means that it's not accelerated.
According Newton's 2nd Law, if the acceleration is zero, the net force on the sliding mass must be zero.
This means that there must be a friction force opposing to the horizontal component of the applied force, equal in magnitude to it:

$F_{appx} = F_{app} * cos \theta = 295 N * cos 35 = 242 N (1)$

In the vertical direction, the block is not accelerated either, so the sum of the normal force and the vertical component of the applied force, must be equal in magnitude to the force of gravity on the block:

$F_{appy} = F_{app} * cos \theta = 295 N * sin 35 = 169 N (2)$

⇒ 169 N + Fn = Fg = 216 N (3)

This means that there must be a normal force equal to the difference between Fappy and Fg, as follows:
Fn = 216 N - 169 N = 47 N (4)

6 0

3 years ago

A motor with a resistance of 320 is connected to a voltage source. Four amps of current flows

cricket20 [7]

Answer:

V = 1280 [V]

Explanation:

To solve this problem we must use ohm's law which tells us that the voltage is equal to the product of the resistance by the current.

Therefore we have:

V = I*R

where:

V = voltage [V] (Units of volts)

I = current = 4 [amp]

R = resistance = 320 [ohms]

V = 4*320

V = 1280 [V]

3 0

3 years ago

A potted plant falls from a window sill and is gaining speed. which one of the following statements is true of the plant?

marishachu [46]

Since the plant is falling, the gravitational energy decreases, so it means b) kinetic energy is increasing.

Hope this helps!! :)

4 0

3 years ago

What is the momentum of a cat(4kg) and running at 1.5 miles

V125BC [204]

Answer:
6kg m/s

Explanation:

Momentum = p=mxv
Momentum = mass x velocity
4kg x 1.5m= 6 kg m/s

4 0

3 years ago

An object at rest does not _____ and an object in motion does not _____, unless an _____ force acts upon it

An object at rest does not ___ and an object in motion does not _, unless an ___ force acts upon it