Answer: v = 
Explanation: q = magnitude of electronic charge = 
mass of an electronic charge =
V= potential difference = 4V
v = velocity of electron
by using the work- energy theorem which states that the kinetic energy of the the electron must equal the work done use in accelerating the electron.
kinetic energy =
, potential energy = qV
hence, 

The mass attached to the spring must be 0.72 kg
Explanation:
The frequency of vibration of a spring-mass system is given by:
(1)
where
k is the spring constant
m is the mass attached to the spring
We can find the spring constant by using Hookes' law:

where
F is the force applied on the spring
x is the stretching of the spring
When a mass of m = 2.82 kg is applied to the spring, the force applied is the weight of the mass, so we have

and using
and
, we find

Now we want the frequency of vibration to be
f = 7.42 Hz
So we can rearrange eq.(1) to find the mass m that we need to attach to the spring:

#LearnwithBrainly
Answer:

Explanation:
F = Magnetic force = 4.11 N
= Net current
= Current in one of the wires = 7.68 A
B = Magnetic field = 0.59 T
= Angle between current and magnetic field = 
= Length of wires = 2.64 m
= Current in the other wire
Magnetic force is given by

Net current is given by

The current I is
.
Momentum = 0.5 * 4 = 2
to conclude the man’s velocity after he throws the piece of equipment, divide
this number by the man’s mass.
v = 2/90
This is about 0.0222 m/s. To know if he can move 6 meters at velocity in
4minutes, use the following equation.
d = v * t, t = 4 * 60 = 240 s
d = 2/90 * 240 = 5⅓ meters.
This is ⅔ of a meter from the spaceship. To know the velocity that he must have
to move 6 meter, use the same equation.
6 = v * 240
v = 6/240
This is about 0.00416 m/s.
His final momentum = 90 * 6/240 = 2.25
To know the velocity of the package, divide this number by the mass of the
package.
v = 2.25/0.5 = 4.5 m/s
The change in internal energy of a system is given by (second law of thermodynamics)

where Q is the heat absorbed by the system and W is the work done on the system.
In order to correctly evaluate the internal energy change, we must be careful with the signs of Q and W:
Q positive -> Q absorbed by the system
Q negative -> Q released by the system
W positive -> W done on the system by the surroundings
W negative -> W done by the system on the surroundings
In our problem, the heat released by the system is

(with negative sign since it is released by the system), and the work done is

still with negative sign because it is performed by the system on the surrounding, so the change in internal energy is