Answer
given,
Length of the string, L = 2 m
speed of the wave , v = 50 m/s
string is stretched between two string
For the waves the nodes must be between the strings
the wavelength is given by

where n is the number of antinodes; n = 1,2,3,...
the frequency expression is given by

now, wavelength calculation
n = 1

λ₁ = 4 m
n = 2

λ₂ = 2 m
n =3

λ₃ = 1.333 m
now, frequency calculation
n = 1


f₁ = 12.5 Hz
n = 2


f₂= 25 Hz
n = 3


f₃ = 37.5 Hz
Hi there!
To solve, we must begin by calculating the total WORK done on the object.
W = F · d (Force · displacement)
Plug in the given values. Remember to convert km to m:
1 km = 1000 m
0.6 km = 600 m
W = 60 · 600 = 36000 J
Now, we can solve for power:
P = W/t
Convert minutes to seconds:
1 min = 60 sec
20 min = 1200 sec
P = 36000/1200 = 30 W ⇒ Choice D.
Answer:

Explanation:
The given data in the question is
Magnetic field : 
Turns : 
Length : 
So, number of turns per unit length :



If current is I , then magnetic field is given by

Also,

Insert the values


The current will be 
The average speed will be:
Total distance travelled divided by time taken
Total distance (in metres)= 80+125+45=250
Total time (minutes) =10
250/10
=25
Thus Mary's average speed is 25 metres per minute.
Answer:
The acceleration of the crate is
.
Explanation:
Given that,
Force, F = 750 N
Mass of the crate, m = 250 kg
The coefficient of friction is 0.12.
We need to find the acceleration of the crate. The net force acting on the crate is given by :

f is frictional force, 

So, the acceleration of the crate is
. Hence, this is the required solution.