Answer:
Magnetic force, 
Explanation:
Given that,
A beryllium-9 ion has a positive charge that is double the charge of a proton, 
Speed of the ion in the magnetic field, 
Its velocity makes an angle of 61° with the direction of the magnetic field at the ion's location.
The magnitude of the field is 0.220 T.
We need to find the magnitude of the magnetic force on the ion. It is given by :

So, the magnitude of magnetic force on the ion is
.
Answer:
Explanation:
Let assume begins movement at zero point, that is, height is equal to zero. The block has an initial linear kinetic energy and no gravitational potential energy and end with no linear kinetic energy, some gravitational potential energy and work losses due to slide friction. In mathematical terms, this system can be model as follows:

Where
are linear kinetic energy, gravitational potential energy and work, respectively.
Answer:
a. k = (1/k₁ + 1/k₂)⁻¹ b. k = (1/k₁ + 1/k₂ + 1/k₃)⁻¹
Explanation:
Since only one force F acts, the force on spring with spring constant k₁ is F = k₁x₁ where x₁ is its extension
the force on spring with spring constant k₂ is F = k₂x₂ where x₁ is its extension
Let F = kx be the force on the equivalent spring with spring constant k and extension x.
The total extension , x = x₁ + x₂
x = F/k = F/k₁ + F/k₂
1/k = 1/k₁ + 1/k₂
k = (1/k₁ + 1/k₂)⁻¹
B
The force on spring with spring constant k₃ is F = k₃x₃ where x₃ is its extension
Let F = kx be the force on the equivalent spring with spring constant k and extension x.
The total extension , x = x₁ + x₂ + x₃
x = F/k = F/k₁ + F/k₂ + F/k₃
1/k = 1/k₁ + 1/k₂ + 1/k₃
k = (1/k₁ + 1/k₂ + 1/k₃)⁻¹
The work done to accelerate the acrobat is given by

where F is the force applied and d the distance of application of the force.
If the barrel is 3.05 m long, then d=3.05 m. Therefore we can find the force: