Answer:
-3.396 m/s or 3.465 m/s
Explanation:
v = Speed of sound in air = 343 m/s
= Relative speed of the singer
f = Observed frequency
f' = Actual frequency
1% change can mean 
From the Doppler effect equation we have

The velocity is -3.396 m/s
when 

The velocity is 3.465 m/s
Answer:
u = - 38.85 m/s^-1
Explanation:
given data:
acceleration = 2.10*10^4 m/s^2
time = 1.85*10^{-3} s
final velocity = 0 m/s
from equation of motion we have following relation
v = u +at
0 = u + 2.10*10^4 *1.85*10^{-3}
0 = u + (21 *1.85)
0 = u + 38.85
u = - 38.85 m/s^-1
negative sign indicate that the ball bounce in opposite directon
Answer:

Explanation:
As we know by first law of thermodynamics that for ideal gas system we have
Heat given = change in internal energy + Work done
so here we will have
Heat given to the system = 2.2 kJ
Q = 2200 J
also we know that work done by the system is given as

so we have



Answer:
Explanation:
During the first .8 s , the elevator is under acceleration . It starts from initial velocity u = 0 , final velocity v = 1.2 m /s , time = .8 s
v = u + at
1.2 = 0 + .8 a
a = 1.2 / .8
= 1.5 m /s²
During the acceleration in upward direction , let reaction force of ground on man be R .
Net force on man = R - mg
Applying Newton's 2 nd law
R - mg = ma
R = m ( g + a )
= 72 ( 9.8 + 1.5 )
= 813.6 N .
This reaction force will be measured by spring scale , so reading of spring scale will be 813.6 N .
Answer:
μ = 0.375
Explanation:
F = Applied force on the trash can = 75 N
W = weight of the trash can = 200 N
f = frictional force acting on trash can
Since the trash can moves at constant speed, force equation for the motion of can is given as
F - f = 0
75 - f = 0
f = 75 N
μ = Coefficient of friction
frictional force is given as
f = μ W
75 = μ (200)
μ = 0.375