Given:
The mass of the halfback is m = 107 kg
The speed of the halfback is v = 8 m/s
To find the momentum.
Explanation:
The momentum of the halfback is

Thus, the momentum of the halfback is 856 kg m/s
Answer:
a. wavelength of the sound, 
b. observed frequecy, 
Given:
speed of sound source,
= 80 m/s
speed of sound in air or vacuum,
= 343 m/s
speed of sound observed,
= 0 m/s
Solution:
From the relation:
v =
(1)
where
v = velocity of sound
= observed frequency of sound
= wavelength
(a) The wavelength of the sound between source and the listener is given by:
(2)
(b) The observed frequency is given by:


(3)
Using eqn (2) and (3):


Answer:
Average speed = 5 m/s
Explanation:
Given the following data;
Distance = 100m
Time = 20 secs
To find the average speed;
Speed = distance/time
Substituting into the formula, we have;
Speed = 100/20
Speed = 5m/s
Therefore, Elsa's average speed is 5 meters per seconds.