Answer: the true statement form the given statements is “the athletes is not doing any work because he does not move weight”
Answer:

Explanation:
When a charge is moving in constant magnetic field and electric field both then the net force on moving charge is vector sum of force due to magnetic field and electric field both
so first the force on the moving charge due to electric field is given by



Now force on moving charge due to magnetic field is given as




Now net force due to both


Answer:
Length of pipe
meter
Explanation:
Speed of a transverse wave on a string

where F is the tension in string and
is the mass per unit length
Thus,

Substituting the given values we get -

Speed of a transverse wave on a string

For third harmonic wave , frequency is equal to

Substituting the given values, we get -

Length of pipe

Substituting the given values we get
for first harmonic wave

Length of pipe
meter