1. 168.1 Hz
To find the apparent frequency heard by the driver in the car, we can use the formula for the Doppler effect:
where
f is the original sound of the horn
v is the speed of sound
is the velocity of the observer (the driver and the car), which is positive if the observer is moving towards the source and negative if it is moving away
is the velocity of the sound source (the train), which is positive if the source is moving away from the observer and negative otherwise
In this problem we have, according to the sign convention used:
Substituting, we find:
2. 
The speed of light can be calculated as
where
d is the distance travelled
t is the time taken
In this problem:
is the total distance travelled by the laser beam (twice the distance between the Earth and the Moon)
t = 2.60 s is the time taken
Substituting in the formula,
Answer:
Explanation:
The variables we know and are given are:
time, t = 20s
Charge, Q = 3x1-^-6 electrons, which is just 3x10^-6C (C stands for Coulombs, which is the unit for Charge)
We need to find the current, I, and since we know Q and t we can substitute these values into the given equation:
I=Q/t (which if you look at what the RHS is saying, its Charge over time, or more literally means the amount of charge passing a point over a period of time)
If we substitute these values, we will get I as:
I = Q / t
I = 3x10^-6 / 20
I = 1.5x10^-7 A
Hope this helps!
Answer:
14.8m
Explanation:
Given parameters:
Initial speed = 17m/s
Unknown:
Maximum height = ?
Solution:
At the maximum height, the final speed will be 0m/s;
We use of the kinematics equation to solve this problem.
V² = U² - 2gH
V is the final velocity
U is the initial velocity
g is the acceleration due to gravity
H is the height
0² = 17² - (2 x 9.8 x h )
0 = 289 - (9.6h)
-289 = -19.6h
h = 14.8m
Answer:
Explanation:
During the swing , the center of mass will go down due to which disc will lose potential energy which will be converted into rotational kinetic energy
mgh = 1/2 I ω² where m is mass of the disc , h is height by which c.m goes down which will be equal to radius of disc , I is moment of inertia of disc about the nail at rim , ω is angular velocity .
mgr = 1/2 x ( 1/2 m r²+ mr²) x ω²
gr = 1/2 x 1/2 r² x ω² + 1/2r² x ω²
g = 1 / 4 x ω² r + 1 / 2 x ω² r
g = 3 x ω² r/ 4
ω² = 4g /3 r
= 4 x 9.8 / 3 x .25
= 52.26
ω = 7.23 rad / s .
The force required is 319 N
Explanation:
The force of static friction is a force that acts an object on a surface, when this object is pushed by another force to put it in motion. The direction of the force of friction is opposite to the direction of the force of push, and its value increases as the force of push increases, up to a maximum value given by:
where
is the coefficient of friction
W is the weight of the object
Therefore, in order to put the object in motion, the force applied must be greater than this value.
For the pile of leaves in this problem, we have:
(coefficient of friction)
(weight of the leaves)
Substituting, we find:
Learn more about force of friction:
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