Answer:
v = 8.4 m/s
Explanation:
The question ays, "A longitudinal wave has a frequency of 200 Hz and a wavelength of 4.2m. What is the speed of the wave?".
Frequency of a wave, f = 200 Hz
Wavelength = 4.2 cm = 0.042 m
We need to find the speed of the wave. The formula for the speed of a wave is given by :

So, the speed of the wave is equal to 8.4 m/s.
 
        
             
        
        
        
Answer:

Explanation:
Given
Mass = 10kg
Velocity = 2m/s
Required
Calculate the momentum of the man
Momentum is calculated as thus
 
or

So; to solve this question; we simply substitute 10kg for mass and 2m/s for velocity in the above formula;
The formula becomes



Hence, the momentum of the man is 
 
        
             
        
        
        
Answer:
4.3 * 10 N
Explanation:
To calculate torque, we multiply the distance from the pivot by the perpendicular (the part of the force that acts at right angles to the displacement vector) component of the force to the displacement vector from the pivot. 
torque  = distance from pivot *  perpendicular force
 170 Nm= 0.4 m * F
F = 425 N = 4.3 * 10 N rounded off to two significant figures
 
        
             
        
        
        
Explanation:
Given Data
Total mass=93.5 kg
Rock mass=0.310 kg
Initially wagon speed=0.540 m/s
rock speed=16.5 m/s
To Find
The speed of the wagon 
Solution
As the wagon rolls, momentum is given as
P=mv
where 
m is mass
v is speed
put the values
P=93.5kg × 0.540 m/s
P =50.49 kg×m/s
Now we have to find the momentum of rock 
momentum of rock = mv
momentum of rock = (0.310kg)×(16.5 m/s)
momentum of rock =5.115 kg×m/s  
From the conservation of momentum we can find the wagons momentum So
wagon momentum=50.49 -5.115 = 45.375 kg×m/s  
Speed of wagon = wagon momentum/(total mass-rock mass)
Speed of wagon=45.375/(93.5-0.310) 
Speed of wagon= 0.487 m/s
Throwing rock backward,
momentum of wagon = 50.49+5.115 = 55.605  kg×m/s
Speed of wagon = wagon momentum/(total mass-rock mass)
speed of wagon = 55.605  kg×m/s/(93.5kg-0.310kg) 
speed of wagon= 0.5967 m/s