Newton's second law states that the resultant of the forces applied to an object is equal to the product between the object's mass and its acceleration:

where in our problem, m is the mass the (child+cart) and a is the acceleration of the system.
We are only concerned about what it happens on the horizontal axis, so there are two forces acting on the cart+child system: the force F of the man pushing it, and the frictional force

acting in the opposite direction. So Newton's second law can be rewritten as

or

since the frictional force is 15 N and we want to achieve an acceleration of

, we can substitute these values to find what is the force the man needs:
Answer:
<h2>Kilometer (km) and micrometer (um) respectively</h2>
Explanation:
<h3>One thousand meters is equal to one kilometer represented as km. </h3>
and
<h3>One thousandth of a meter mean 1/1000 m which implies one thousands part of a meter which is equal to micro meter and represented as um.</h3>
If the boat is floating, then it's just sitting there, and not accelerating
up or down. That means the vertical forces on it must be balanced.
So if its weight (acting downward) is 100 newtons, then the buoyant
force on it (acting upward) must also be 100 newtons.
Answer:
Correct answer: C. 50 cm
Explanation:
Given data:
The distance of the object from the top of the concave mirror o = 50.0 cm
The magnitude of the concave mirror focal length 25.0 cm.
Required : Image distance d = ?
If we know the focal length we can calculate the center of the curve of the mirror
r = 2 · f = 2 · 25 = 50 cm
If we know the theory of spherical mirrors and the construction of figures then we know that when an object is placed in the center of the curve, there is also a image in the center of the curve that is inverted, real and the same size as the object.
We conclude that the image distance is 50 cm.
We will now prove this using the formula:
1/f = 1/o + 1/d => 1/d = 1/f - 1/o = 1/25 - 1/50 = 2/50 - 1/50 = 1/50
1/d = 1/50 => d = 50 cm
God is with you!!!