Answer:a & d
Explanation:
Given
Net force on object is zero i.e. 

if net acceleration is zero therefore change in velocity is zero i.e. velocity is constant
It is not necessary that when an object is at rest acceleration on it is zero for example during Simple harmonic motion of spring mass system when mass is at maximum amplitude i.e. momentarily at rest then its acceleration is maximum.
Answer:
The recoil speed of the man and rifle is
.
Explanation:
The expression for the force in terms of mg is as follows;
F=mg
Here, m is the mass and acceleration due to gravity.
Rearrange the expression for mass.

Calculate the combined mass of the man and rifle.

Put
.


The expression for the conservation of momentum is as follows as;

Here,
is the mass of the man and rifle,
is the mass of the rifle,
are the initial velocities of the man and bullet and
are the final velocities of the man and rifle and rifle.
It is given in the problem that a rifle with a weight of 25 N fires a 4.5-g bullet with a speed of 240 m/s.
Convert mass of rifle from gram to kilogram.


Put
,
,
,
and
.




Therefore, the recoil speed of the man and rifle is
.
Answer:
Light travels as a wave. But unlike sound waves or water waves, it does not need any matter or material to carry its energy along. This means that light can travel through a vacuum—a completely airless space. (Sound, on the other hand, must travel through a solid, a liquid, or a gas.)
Explanation:
The metalcore is the central component of any metal that is covered by wires. Metalcore is found in the X denoted area.
<h3>What is a solenoid?</h3>
A solenoid is a coil of wire that conducts an electric current. A solenoid is an electromagnet made out of a wire or helical coil.
When an electric current is sent through the coil, it produces a magnetic field. A solenoid is a coil that generates a magnetic field when an electric current passes through it.
When a conductive wire is used to build a loop, a solenoid is formed.
Hence the metalcore is found in the given X area.
To learn more about the solenoid refer to the link ;
brainly.com/question/16015159