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3 years ago

A rock is thrown straight up. What is the net external force acting on the rock when it is at the top of its trajectory?

Physics

1 answer:

Korolek [52]3 years ago

6 0

Answer:

Net external force acting on the rock when it is at the top of its trajectory is force due to gravity (mg).

Explanation:

The forces acting on a rock thrown up are force due to gravity and air resistance. Air resistance is directly proportional to velocity of rock, when velocity is zero air resistance is zero. When it is at the top of its trajectory its velocity is zero. So air resistance is also zero. Hence only gravitational force acts on the rock.

Net external force acting on the rock when it is at the top of its trajectory is force due to gravity (mg).

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An unstretched spring has a length of 10. centimeters. When the spring is stretched by a force of 16 newtons, its length is incr

Fed [463]

Answer:

The spring constant of this spring is 200 N/m.

Explanation:

Given:

Original unstretched length of the spring (x₀) = 10 cm =0.10 m [1 cm =0.01 m]

Stretched length of the spring (x₁) = 18 cm = 0.18 cm

Force acting on the spring (F) = 16 N

Spring constant of the spring (k) = ?

First let us find the change in length of the spring or the elongation caused in the spring due to the applied force.

So, Change in length = Final length - Initial length

$\Delta x = x_1-x_0=0.18-0.10=0.08\ m$

Now, restoring force acting on the spring is directly related to its elongation or compression as:

$F=k\Delta x$

Rewriting in terms of 'k', we get:

$k=\dfrac{F}{\Delta x}$

Now, plug in the given values and solve for 'k'. This gives,

$k=\frac{16\ N}{0.08\ m}\\\\k=200\ N/m$

Therefore, the spring constant of this spring is 200 N/m.

5 0

3 years ago

A car is designed to get its energy from a rotating

nydimaria [60]

Answer:

(a). The kinetic energy stored in the fly wheel is 46.88 MJ.

(b). The time is 1.163 hours.

Explanation:

Given that,

Radius = 1.50 m

Mass = 475 kg

Power $P= 15.0 hp = 15.0\times746=11190 watt$

Rotational speed = 4000 rev/min

We need to calculate the moment of inertia

Using formula of moment of inertia

$I=\dfrac{1}{2}mr^2$

Put the value into the formula

$I=\dfrac{1}{2}\times475\times(1.50)^2$

$I=534.375\ kg m^2$

(a). We need to calculate the kinetic energy stored in the fly wheel

Using formula of K.E

$K.E=\dfrac{1}{2}I\omega^2$

Put the value into the formula

$K.E = \dfrac{1}{2}\times534.375\times(4000\times\dfrac{2\pi}{60})^2$

$K.E=46880620.9\ J$

$K.E =46.88\times10^{6}\ J$

$K.E =46.88\ MJ$

(b). We need to calculate the length of time the car could run before the flywheel would have to be brought backup to speed

Using formula of time

$t=\dfrac{46.88\times10^{6}}{11190}$

$t=4189.45\ sec$

$t=1.163\ hours$

Hence, (a). The kinetic energy stored in the fly wheel is 46.88 MJ.

(b). The time is 1.163 hours.

3 0

3 years ago

Two ships leave a harbor at the same time, traveling on courses that have an angle of 110∘ between them. If the first ship trave

Allushta [10]

Answer:

49.07 miles

Explanation:

Angle between two ships = 110° = θ

First ship speed = 22 mph

Second ship speed = 34 mph

Distance covered by first ship after 1.2 hours = 22×1.2 = 26.4 miles = b

Distance covered by second ship after 1.2 hours = 34×1.2 = 40.8 miles = c

Here the angle between the two sides of a triangle is 110° so from the law of cosines we get

a² = b²+c²-2bc cosθ

⇒a² = 26.4²+40.8²-2×26.4×40.8 cos110

⇒a² = 2408.4

⇒a = 49.07 miles

6 0

3 years ago

PROJECTILE MOTION-Why isn't there any accelertion in the x direction while there is an acceleration of -g in the y direction? ..

Ahat [919]

There is no acceleration of g in the x direction because the gravitational acceleration points downward. Also, on most studies we ignore the tidal forces since we are dealing with small bodies compared to the size of the earth.

I hope my answer has come to your help. Thank you for posting your question here in Brainly. We hope to answer more of your questions and inquiries soon. Have a nice day ahead!

5 0

3 years ago

Which object experiences the greatest gravitational force? A)car B)fire truck C)plane D)human

Svetlanka [38]

Answer: C Plane

Explanation: According to Newton's law, gravitational force is proportional to the product of masses and inversely proportional to the square of distance between them.

Gravitational force depends on mass. The bigger the mass, the more the magnitude of the gravitational force. Since plane is assume to have the highest mass in the options, we can therefore conclude that plane will experience the highest gravitational force.

3 0

3 years ago