According to Newton's second law,

There are two forces acting on the person standing on the scale in the elevator. Those two forces are the person's weight due to gravity (which acts in a downward direction), and the normal force from standing on the scale (which acts in an upward direction).  So, the net force equation can be written as:

 represents the person's weight, which was given in the problem to be 700 N.   is the normal force due to standing on the scale; this is what we are trying to find, because it is what the scale would read. We subtract the two forces because they point in opposite directions, and so one must be positive and the other negative.

We also know the acceleration, , is .

We were not given the mass of the person, but we can find it because we know the person's weight is 700 N. The equation that relates a person's mass to their weight near the surface of the Earth is:

Now we can solve for the normal force by using the mass we found in the original equation above:

The answer is exemplified by the centripetal force equation: 

.

When we combine the units of each of the equation's components, we arrive at

 which, when simplified, becomes 

First, lets identify the given information:

Since this is a collision problem, we can apply the law of conservation of momentum:

Because Car 2 is initially at rest, this equation can be simplified:

The equation can then be rearranged to solve for the mass of Car 2:

 By plugging in the known values, we can determine the mass of Car 2:

To calculate the pressure  on the floor, we need to know the force  acting on the floor, as well as the area  over which it acts.

The force acting is simply the weight of the cube, 

The area is the area of one side of the cube as it rests on the floor, 

Therefore, the pressure  is given as:

Plug in known values and solve.

Once the spacecraft had reached a constant speed, so had it's occupants. Thus, the astronauts were also moving at and they were experiencing no forces from their seats.

Thus, the astronauts were experiencing zero net force.

 and  cancel each other out in the horizontal direction due to the fact that they are equal and opposite about the vertical axis. Now that the resultant force in the x-direction is zero, we must find what  must be in order to zero out the other two forces' y-components, which are:

These forces are pointing in the positive y-direction (pulling the object up). Therefore, in order to have a resultant force of zero in the vertical direction, there must be a downward force of

Since we are asked for the magnitude, we are not particularly concerned with the sign of this value.

In these conceptual problems, it is always best to draw an accurate force diagram. In string problems, there is always a tension force, and here, it is causing the circular motion. The tension force causes the lasso to swing in a circle and pulls it toward the center of the circle. 

To answer this question, we'll need to be familiar with Isaac Newton's fundamental laws of physics, which forms the basis of classical mechanics.

Newton's first law states that an object in motion will remain in that state of motion indefinitely, unless an outside force acts on this object.

Newton's second law can be stated as follows:

This expression tells us that the acceleration experienced by an object is directly proportional to the applied force and inversely proportional to the object's mass.

Newton's third law states that for every action, there is always an equal and opposite reaction. Another way of saying this is that if one object were to exert a force on a second object, then the second object would exert the same force against the first object.

One of the answer choices states the following

"In order for an object to be in motion, a force needs to act on it."

While this may seem intuitive based on our everyday experience, and it may also show some resemblance to Newton's first law, this statement is actually incorrect. Force is not responsible for motion - force is responsible for changes in motion.

The force due to kinetic friction is calculated by the equation 

where  is the normal force on the box from the ground. The frictional force is in the opposite direction of the force applied by you and your friend. Therefore, the net force can be calculated: