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Zielflug [23.3K]
3 years ago
14

The distance traveled, in feet, of a ball dropped from a tall building is modeled by the equation d(t) = 16t2 where d equals the

distance traveled at time t seconds and t equals the time in seconds. What does the average rate of change of d(t) from t = 2 to t = 5 represent?
A. The ball travels an average distance of 112 feet from 2 seconds to 5 seconds.

B. The ball falls down with an average speed of 48 feet per second from 2 seconds to 5 seconds.

C. The ball falls down with an average speed of 112 feet per second from 2 seconds to 5 seconds.

D. The ball travels an average distance of 48 feet from 2 seconds to 5 seconds.
Physics
1 answer:
Ainat [17]3 years ago
6 0
When  t=2, the ball has fallen     d(2) = 16 (2²) = 64 feet .

When  t=5, the ball has fallen     d(5) = 16 (5²) = 400 feet .

Distance fallen from  t=2  until  t=5  is  (400 - 64) = 336 feet.

Time period between  t=2  until  t=5  is  (5 - 2) = 3 seconds.

Average speed of the ball from  t=2  until  t=5  is

                 (distance covered) / (time to cover the distance)

             =            336 feet        /        3 seconds       =  112 feet per second.

That's what choice-C says.        
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Two cars are involved in a crash (no one was hurt in the accident). If
Lunna [17]
Im fairly certain that the answer would be D, and this is because of the law of conservation of energy/momentum.
8 0
3 years ago
two point charges of 5*10^-19 C and 20*10^-19C are separated by a distance of 2m. at which point on the line joining them will h
Aneli [31]

Answer:

On that line segment between the two charges, at approximately 0.7\; \rm m away from the smaller charge (the one with a magnitude of 5 \times 10^{-19}\; \rm C,) and approximately 1.3\; \rm m from the larger charge (the one with a magnitude of 20 \times 10^{-19}\; \rm C.)

Explanation:

Each of the two point charges generate an electric field. These two fields overlap at all points in the space around the two point charges. At each point in that region, the actual electric field will be the sum of the field vectors of these two electric fields.

Let k denote the Coulomb constant, and let q denote the size of a point charge. At a distance of r away from the charge, the electric field due to this point charge will be:

\displaystyle E = \frac{k\, q}{r^2}.

At the point (or points) where the electric field is zero, the size of the net electrostatic force on any test charge should also be zero.

Consider a positive test charge placed on the line joining the two point charges in this question. Both of the two point charges here are positive. They will both repel the positive test charge regardless of the position of this test charge.

When the test charge is on the same side of both point charges, both point charges will push the test charge in the same direction. As a result, the two electric forces (due to the two point charges) will not balance each other, and the net electric force on the test charge will be non-zero.  

On the other hand, when the test charge is between the two point charges, the electric forces due to the two point charges will counteract each other. This force should be zero at some point in that region.

Keep in mind that the electric field at a point is zero only if the electric force on any test charge at that position is zero. Therefore, among the three sections, the line segment between the two point charges is the only place where the electric field could be zero.

Let q_1 = 5\times 10^{-19}\; \rm C and q_2 = 20 \times 10^{-19}\; \rm C. Assume that the electric field is zero at r meters to the right of the 5\times 10^{-19}\; \rm C point charge. That would be (2 - r) meters to the left of the 20 \times 10^{-19}\; \rm C point charge. (Since this point should be between the two point charges, 0 < r < 2.)

The electric field due to q_1 = 5\times 10^{-19}\; \rm C would have a magnitude of:

\displaystyle | E_1 | = \frac{k\cdot q_1}{r^2}.

The electric field due to q_2 = 20 \times 10^{-19}\; \rm C would have a magnitude of:

\displaystyle | E_2 | = \frac{k\cdot q_2}{(2 - r)^2}.

Note that at all point in this section, the two electric fields E_1 and E_2 will be acting in opposite directions. At the point where the two electric fields balance each other precisely, | E_1 | = | E_2 |. That's where the actual electric field is zero.

| E_1 | = | E_2 | means that \displaystyle \frac{k\cdot q_1}{r^2} = \frac{k\cdot q_2}{(2 - r)^2}.

Simplify this expression and solve for r:

\displaystyle q_1\, (2 - r)^2 - q_2 \, r^2 = 0.

\displaystyle 5\times (2 - r)^2 - 20\, r^2 = 0.

Either r = -2 or \displaystyle r = \frac{2}{3}\approx 0.67 will satisfy this equation. However, since this point (the point where the actual electric field is zero) should be between the two point charges, 0 < r < 2. Therefore, (-2) isn't a valid value for r in this context.

As a result, the electric field is zero at the point approximately 0.67\; \rm m away the 5\times 10^{-19}\; \rm C charge, and approximately 2 - 0.67 \approx 1.3\; \rm m away from the 20 \times 10^{-19}\; \rm C charge.

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A ball is thrown straight up with an initial speed of 50 ms how high does it go?
gavmur [86]
h_{max}=\frac{v_0^2}{2g}=125m (g=10\frac{m}{s^2})
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A negative velocity, approaching zero, represents a negative acceleration. True or False
ruslelena [56]

Answer:

False.

Explanation:

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