A constant friction force of 21 N acts on a 63-kg skier for 25 s on level snow. What is the skier’s change in velocity?

Mariana [72]

42) The sailboat travels east with velocity $v_e=30 mph$ , while the current moves south with speed $v_s=30 mph$ . Since the two velocities are perpendicular to each other, he resultant velocity will be given by the Pytagorean theorem:
$v= \sqrt{v_e^2+v_s^2}= \sqrt{(30)^2+(30)^2}=42 mph$
and the direction is in between the two original directions, therefore south-east. So, the correct answer is
D) 42 mph southeast

43) Since the light moves by uniform motion, we can calculate the distance corresponding to one light year by using the basic relationship between velocity, space and time. In fact, we know the velocity:
$v=300,000,000 m/s=3 \cdot 10^8 m/s$
and the time is one year, corresponding to:
$t=32,000,000 s=3.2 \cdot 10^7 s$
therefore, the distance corresponding to one light year is:
$S=vt=(3\cdot 10^8 m/s)(3.2 \cdot 10^7 s)=9.6 \cdot 10^{15}m$
Therefore, the correct answer is D.

44) For the purpose of the problem, we can assume that the light travels instantaneously from the flash to us (because the distances involved are very small), so the time between the flash and the thunder corresponds to the time it took for the sound to travel to us.
The speed of sound is
$v=1100 ft/s=750 mph=335 m/s$
And since the time between the flash and the thunder is t=3 s, the distance is
$S=vt=(335 m/s)(3 s)=1005 m=0.62 miles$
Therefore, the correct answer is A) 3/5 mile.

6 0

3 years ago

A stereo speaker is rated at P1000 = 52 W of output at 1000 Hz. At 20 Hz, the sound intensity level LaTeX: \betaβ decreases by 1

baherus [9]

Answer:

The value of the power is $P_c = 38.55 \ W$

Explanation:

From the question we are told that

The power rating $P_{1000} =P_b= 52 \ W$

The frequency is $f = 1000 \ Hz$

The frequency at which the sound intensity decreases $f_k = 20 \ Hz$

The decrease in intensity is by $\beta = 1.3 dB$

Generally the initial intensity of the speaker is mathematically represented as

$\beta_1 = 10 log_{10} [\frac{P_b}{P_a} ]$

Generally the intensity of the speaker after it has been decreased is

$\beta_2 = 10 log_{10} [\frac{P_c}{P_a} ]$

So

$\beta_1-\beta_2 = 10 log_{10} [\frac{P_c}{P_a} ]- 10 log_{10} [\frac{P_b}{P_a} ]$

=> $\beta = 10 log_{10} [\frac{P_c}{P_a} ]- 10 log_{10} [\frac{P_b}{P_a} ]= 1.3$

=> $\beta =10log_{10} [\frac{\frac{P_b}{P_a}}{\frac{P_c}{P_a}} ] = 1.3$

=> $\beta =10log_{10} [\frac{P_b}{P_c} ] = 1.3$

=> $10log_{10} [\frac{P_b}{P_c} ] = 1.3$

=> $log_{10} [\frac{P_b}{P_c} ] = 0.13$

taking atilog of both sides

$[\frac{P_b}{P_c} ] = 10^{0.13}$

=> $[\frac{52}{P_c} ] = 10^{0.13}$

=> $P_c = \frac{52}{1.34896}$

=> $P_c = 38.55 \ W$

3 0

3 years ago

A child is sliding on a sled at 1.3 m/s to the right. You stop the sled by pushing on it for 0.80 s in a direction opposite to i

Shalnov [3]

Answer:

find acceleration first

a = vf - vi / t

a = 0 - 1.5 / 0.5s (vf is zero)

a = -3 (negative sign indicates that acceleration is decreasing)

so F=ma

F = 35 x -3

F = -105 N (here negative sign indicates that u have to apply a force opposite to the boy's direction i.e from the left or towards the right)

Explanation:

3 0

4 years ago

A negatively charged object has _______________ electrons than an object that is neutral.

Free_Kalibri [48]

Answer:

more electrons

Explanation:

4 0

3 years ago

If you told a policeman about a car traveling 44.704 m/s (100 mph) that was traveling in an eastward direction, you would be des

Tpy6a [65]

Answer:

Velocity

Explanation:

You would be describing the velocity of the car.

Velocity in physics is defined as Vector quantity that describes the displacement of an object with respect to the time it takes to attain it. Displacement is the addition of direction to the speed of an object. The displacement is noted in the question, "traveling eastward". While it is stated that the car travels at 44.704 m/s. Ordinarily, it would have been tagged speed, if not for the direction added to it which makes it velocity.

I hope you understand.

5 0

3 years ago