The second, fourth, and seventh answers apply. Energy in a closed system is conserved, but it can change form
Answer:
showm
Explanation:
Consider a dipole having magnetic moment 'm' is placed in magnetic field then the torque exerted by the field on the dipole is
Now to rotate the dipole in the field to its final position the work required to be done is
Minimum energy mB is for the case when m is anti parallel to B.
Minimum energy -mB is for the case when m is parallel to B.
A large body of matter with no definite shape.
The SI unit is-kilogram(kg).
Solution :
Given :
Mass of the baseball, m = 200 g
Velocity of the baseball, u = -30 m/s
Mass of the baseball after struck by the bat, M = 900 g
Velocity of the baseball after struck by the bat, v = 47 m/s
According to the conservation of momentum,
(900 x 47) + (200 x -30) = (900 x ) + (200 x )
36300 = (900 x ) + (200 x )
..............(i)
The mathematical expression for the conservation of kinetic energy is
................(ii)
Substituting (i) in (ii)
Solving the equation, we get
The negative velocity is neglected.
Therefore, substituting 96 m/s for in (i), we get
= 19
Thus, only impulse of importance is used to find final velocity.
By Newton's second law, the net vertical force acting on the object is 0, so that
<em>n</em> - <em>w</em> = 0
where <em>n</em> = magnitude of the normal force of the surface pushing up on the object, and <em>w</em> = weight of the object. Hence <em>n</em> = <em>w</em> = <em>mg</em> = 196 N, where <em>m</em> = 20 kg and <em>g</em> = 9.80 m/s².
The force of static friction exerts up to 80 N on the object, since that's the minimum required force needed to get it moving, which means the coefficient of <u>static</u> friction <em>µ</em> is such that
80 N = <em>µ</em> (196 N) → <em>µ</em> = (80 N)/(196 N) ≈ 0.408
Moving at constant speed, there is a kinetic friction force of 40 N opposing the object's motion, so that the coefficient of <u>kinetic</u> friction <em>ν</em> is
40 N = <em>ν</em> (196 N) → <em>ν</em> = (40 N)/(196 N) ≈ 0.204
And so the closest answer is C.
(Note: <em>µ</em> and <em>ν</em> are the Greek letters mu and nu)