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2 years ago

A boy is trying to roll a bowling ball up a hill, as shown in the image below. If

Physics

1 answer:

kherson [118]2 years ago

4 0

The minimum initial velocity that the ball must have for it to reach the top of the hill is 21 m/s. The correct option is D.

<h3>What is mechanical energy?</h3>

The mechanical energy is the sum of kinetic energy and the potential energy of an object at any instant of time.

M.E = KE +PE

A boy is trying to roll a bowling ball up a hill. The friction is ignored. The ball must have to reach the top of the hill with a velocity. The acceleration due to gravity, g = 9.8 m/s²

The conservation of energy principle states that total mechanical energy remains conserved in all situations where there is no external force acting on the system.

M.E bottom of hill = M.E on top of hill

Kinetic energy + Potential energy = Kinetic energy + Potential energy

1/2 mu² + 0 = 0 + mgh

At the top of hill, the velocity will become zero. So, final kinetic energy is zero.

Substituting the values, we have

1/2 x u² = 9.8 x 22.5

u = sqrt [2 x9.8 x 22.5 ]

u= 21 m/s

Thus, the minimum initial velocity that the ball must have for it to reach the top of the hill is 21 m/s.

Learn more about mechanical energy.

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2 years ago

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Three cars (car F, car G, and car H) are moving with the same speed and slam on their brakes. The most massive car is car F, and

Crazy boy [7]

To solve this problem it is necessary to apply the concepts related to Normal Force, frictional force, kinematic equations of motion and Newton's second law.

From the kinematic equations of motion we know that the relationship of acceleration, velocity and distance is given by

$v_f^2=v_i^2+2ax$

Where,

$v_f =$ Final velocity

$v_i =$ Initial Velocity

a = Acceleration

x = Displacement

Acceleration can be expressed in terms of the drag coefficient by means of

$F_f = \mu_k (mg) \rightarrow$ Frictional Force

$F = ma \rightarrow$ Force by Newton's second Law

Where,

m = mass

a= acceleration

$\mu_k =$ Kinetic frictional coefficient

g = Gravity

Equating both equation we have that

$F_f = F$

$\mu_k mg=ma$

$a = \mu_k g$

Therefore,

$v_f^2=v_i^2+2ax$

$0=v_i^2+2(\mu_k g)x$

Re-arrange to find x,

$x = \frac{v_i^2}{2(-\mu_k g)}$

The distance traveled by the car depends on the coefficient of kinetic friction, acceleration due to gravity and initial velocity, therefore the three cars will stop at the same distance.

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3 years ago

A property unique to a conducting substance that determines its resistance is called:

elena-s [515]

Answer:

B. Resistivity

Explanation:

Resistance offered by a substance of unit area per unit length.

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3 years ago

Calculate two stars appear to you to have the same brightness. if star a is 7.00 light-years away from you, while star b is 15.0

vagabundo [1.1K]

It is eight times more than the star A.

<h3>What is luminosity and on which it depends?</h3>

The luminosity of an object is a measure of its intrinsic brightness and is defined as the amount of energy the object emits in a fixed time.

luminousity depends upon the two factors are:

1) The star's actual brightness

Some stars are naturally more luminous than others ,so the brightness level from one star to next star is significantly different.

2) The star distance from us

The more distance of an object the dimmer it appears.

Energy emitted = sAT⁴

where s is stefan constant

A is surface area and T is temperature .

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9 months ago

If a car goes down Lake at 30 miles per hour how far will it go in 0.25 hours?

kati45 [8]

Answer:

7.5 miles

Explanation:

0.25 hours=15minutes.

So you do

30 miles=60minutes

x =15minutes

cross multiply

Ans-7.5

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3 years ago