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3 years ago

A ball is thrown straight up. What are the velocity and acceleration of the ball at the highest point in its path?

Physics

1 answer:

zubka84 [21]3 years ago

8 0

Answer:

b. v = 0, a = 9.8 m/s² down.

Explanation:

Hi there!

The acceleration of gravity is always directed to the ground (down) and, near the surface of the earth, has a constant value of 9.8 m/s². Since the answer "b" is the only option with an acceleration of 9.8 m/s² directed downwards, that would solve the exercise. But why is the velocity zero at the highest point?

Let´s take a look at the height function:

h(t) = h0 + v0 · t + 1/2 g · t²

Where

h0 = initial height

v0 = initial velocity

t = time

g = acceleration due to gravity

Notice that the function is a negative parabola if we consider downward as negative (in that case "g" would be negative). Then, the function has a maximum (the highest point) at the vertex of the parabola. At the maximum point, the slope of the tangent line to the function is zero, because the tangent line is horizontal at a maximum point. The slope of the tangent line to the function is the rate of change of height with respect to time, i.e, the velocity. Then, the velocity is zero at the maximum height.

Another way to see it (without calculus):

When the ball is going up, the velocity vector points up and the velocity is positive. After reaching the maximum height, the velocity vector points down and is negative (the ball starts to fall). At the maximum height, the velocity vector changed its direction from positive to negative, then at that point, the velocity vector has to be zero.

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A block of mass 27.00 kg sits on a horizontal surface with, coefficient of kinetic

zhannawk [14.2K]

Answer:

The force is $F = 172 \ N$

Explanation:

From the question we are told that

The mass of the block is $m_b = 27.0 \ kg$

The coefficient of static friction is $\mu_s = 0.65$

The coefficient of kinetic friction is $\mu_k = 0.50$

The normal force acting on the block is

$N = m * g$

substituting values

$N = 27 * 9.8$

$N = 294.6 \ N$

Given that the force we are to find is the force required to get the block to start moving then the force acting against this force is the static frictional force which is mathematically evaluated as

$F_f = \mu_s * N$

substituting values

$F_f = 0.65 * 264.6$

$F_f = 172 \ N$

Now for this block to move the force require is equal to $F_f$ i.e

$F= F_f$

=> $F = 172 \ N$

5 0

3 years ago

In a perfectly elastic collision between two perfectly rigid objects

ipn [44]

Both the total momentum and the total kinetic energy are conserved

Explanation:

- In a collision between two or more objects, if there are no external forces acting on the system (isolated system), the total momentum of the objects is always conserved. This is called principle of conservation of momentum, and can be written as follows:

$mu+MU = mv+MV$

where

m, M are the masses of the two objects

u, U are the initial velocities of the two objects

v, V are the final velocities of the two objects

- The total kinetic energy, however, is not always conserved. In fact, we have two types of collision:

1) In a perfectly elastic collision, the total kinetic energy of the objects is conserved. This means that we can write the following equation:

$\frac{1}{2}mu^2 + \frac{1}{2}MU^2 = \frac{1}{2}mv^2+\frac{1}{2}MV^2$

2) In an inelastic collision, the total kinetic energy of the object is NOT conserved. This means that part of the total kinetic energy is "lost", converted into other forms of energy (mainly thermal energy, due to the presence of frictional forces within the system). The most extreme case is called perfectly inelastic collision, in which the two objects stick together after the collision, and there is the maximum loss of kinetic energy.

Learn more about collisions:

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7 0

3 years ago

Suppose you need your silicon circuit element to run continuously for 3 minutes before it shuts off long enough to cool back dow

Zigmanuir [339]

The maximum rate at which energy can be added to the circuit element mathematically given as

$MER=5.044 \times 10^{-4} \mathrm{~J} / \mathrm{sec}$

<h3>What is the maximum rate at which energy can be added to the circuit element?</h3>

Generally, the equation for P is mathematically given as

$P=\ln s \frac{\Delta T}{\Delta t}$

Therefore

$Rate\ of\ Change\ of\ Temp =\frac{p}{lnS}$

$\frac{p}{lnS}=\frac{7.4 \times 10^{-3}}{23 \times 10^{-6} \times 705}$

$\frac{p}{lnS}=0.456^{\circ \mathrm{c}} / \mathrm{sec}$

Max temp Change

$MaxT=5.6^{\circ} \mathrm{C}$

$\text { time }=3 \times 60$

t=180s

In conclusion, Max Energy Rate

$MER =23 \times 10^{-6} \times \frac{301 \times 5.6}{180}$

$MER=5.044 \times 10^{-4} \mathrm{~J} / \mathrm{sec}$

Read more about Energy

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3 0

1 year ago

An ac generator has a maximum emf output of 150 V. What is the rms current in the circuit when the generator is connected to a 3

natima [27]

This is an insidious question. Quite frankly, I would not have
expected to see it here on Brainly. But I'm ready to play the
cards that you have dealt me.

None of the choices offered is a correct solution.

If the output of the AC generator is nice and sinusoidal, and
its maximum (peak) emf is 150 volts, then its RMS emf is

   (1/2) (150) (√2) = 106.07 volts.

The resistor's dissipation is

   Power = (current) x (voltage) .

If the resistor is dissipating its full rated 35W, then

   35W = (current) x (106.07 V)

Divide each side by 106.07 V:

   RMS Current = (35W) / (106.07 V) = 0.33 Ampere .
_________________________________________

Looking over the choices offered . . .

The largest choice ... 3.1 A ... is the current in a resistor
that is dissipating 35W if the voltage is

   (35W / 3.1A) = 11.29 volts .

The smallest choice ... 1.2 A ... is the current in a resistor
that is dissipating 35W if the voltage is

   (35W / 1.2A) = 29.17 volts .

Whatever you meant the so-called "150 V" of the generator
to represent ... whether the RMS sinusoidal, peak sinusoidal,
peak square-wave, RMS square-wave, DC, average, etc. ...
none of the choices for current, in combination with any of these
generators, would dissipate 35W.

3 0

3 years ago

How does the sun impact land at different latitudes?

Masja [62]

The radiation of the solar rays of the sun can damage and heat up land closer but at the same time cool because of the atmosphere

5 0

2 years ago