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3 years ago

I have a question regarding friction in rolling without slipping.

Physics

1 answer:

Solnce55 [7]3 years ago

4 0

Explanation:

They probably put "rolls without slipping" in there to indicate that there is no loss in friction; or that the friction is constant throughout the movement of the disk. So it's more of a contingency part of the explanation of the problem.

(Remember how earlier on in Physics lessons, we see "ignore friction" written into problems; it just removes the "What about [ ]?" question for anyone who might ask.)

In this case, you can't ignore friction because the disk wouldn't roll without it.

As far as friction producing a torque... I would say that friction is a result of the torque in this case. And because the point of contact is, presumably, the ground, the friction is tangential to the disk. Meaning the friction is linear and has no angular component.

(You could probably argue that by Newton's 3rd Law there should be some opposing torque, but I think that's outside of the scope of this problem.)

Hopefully this helps clear up the misunderstanding for you.

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Two bodies, A and B, have equal kinetic energies. The mass of A is nine times that of B. The ratio of the momentum of A to that

mylen [45]

Answer:

D. 3 : 1

Explanation:

Let suppose that A and B are particles. From statement we know that $K_{A} = K_{B }$ (same kinetic energy) and $m_{A} = 9\cdot m_{B}$ . Then,

$K_{A} = K_{B}$

$\frac{1}{2}\cdot m_{A}\cdot v_{A}^{2} = \frac{1}{2}\cdot m_{B}\cdot v_{B}^{2}$

$m_{A} \cdot v_{A}^{2} = m_{B}\cdot v_{B}^{2}$

$\frac{v_{B}}{v_{A}} = \sqrt{\frac{m_{A}}{m_{B}} }$

$\frac{v_{B}}{v_{A}} = 3$

And the ratio of the momentum of A to the momentum of B is:

$r = \frac{m_{A}\cdot v_{A}}{m_{B}\cdot v_{B}}$

$r = 9\times \frac{1}{3}$

$r = 3$

Hence, the correct answer is D.

4 0

3 years ago

A car is traveling in a race.The car went from the initial velocity of 35 to the final velocity of 65 in 5 seconds what is the a

Ann [662]

Answer:

Acceleration = 6m/s²

Explanation:

<u>Given the following data;</u>

Initial velocity = 35m/s

Final velocity = 65m/s

Time = 5 seconds

To find the acceleration;

In physics, acceleration can be defined as the rate of change of the velocity of an object with respect to time.

This simply means that, acceleration is given by the subtraction of initial velocity from the final velocity all over time.

Mathematically, acceleration is given by the equation;

$Acceleration (a) = \frac{final \; velocity - initial \; velocity}{time}$

Where,

a is acceleration measured in $ms^{-2}$
v and u is final and initial velocity respectively, measured in $ms^{-1}$
t is time measured in seconds.

Substituting into the equation, we have

$a = \frac{65 - 35}{5}$

$a = \frac{30}{5}$

<em>Acceleration = 6m/s²</em>

7 0

3 years ago

The current and the potential difference in an inductor are in phase. B. The current lags the potential difference by π/2 in an

slava [35]

Answer:

The current lags the potential difference by π/2 in an inductor

Explanation:

The potential difference leads to the current by $\frac{\pi}{2}$ . Alternate signals such as current and voltage -in this case- are periodic, this means that this signals are repeated at fixed spaces of time. Thus, In an inductor the current lags the potential difference by $\frac{\pi}{2}$ .