We are given a box that slides up a ramp. To determine the force of friction we will use the following relationship:

Where.

To determine the Normal force we will add the forces in the direction perpendicular to the ramp, we will call this direction the y-direction as shown in the following diagram:
In the diagram we have:

Adding the forces in the y-direction we get:

Since there is no movement in the y-direction the sum of forces must be equal to zero:

Now we solve for the normal force:

To determine the y-component of the weight we will use the trigonometric function cosine:

Now we multiply both sides by "mg":

Now we substitute this value in the expression for the normal force:

Now we substitute this in the expression for the friction force:

Now we substitute the given values:

Solving the operations:

Therefore, the force of friction is 15.01 Newtons.
Answer:
A
Explanation:
If you do B, the wagon slows down due to friction
If you do C, it would slow down the wagon by half
If you do D, it would slow it down, due to there being more weight but same force.
Answer:
13 m/s
Explanation:
I assume we are ignoring friction.
The boy's PE will all be converted to KE at the bottom of the hill.
to find PE = mgh we need to know h
h = 50 sin 10 = 8.68 meters
then: PE = 20 * 9.81 * 8.68 =<u> 1703.49</u> j
KE = 1/2 m v^2 = <u>1703 .49</u>
v = 13 m/s
Answer:
v=32.9m/s
Explanation:
The acceleration needed to mantain a circular motion of radius r and speed v is given by the equation 
This is the centripetal acceleration. The person will feel what is called a centrifugal acceleration, of the same value, because he is not in an inertial frame (thus subject to fictitious forces, product of inertia).
We want to know the speed of his head when it is subject to 12.5 times the value of the acceleration of gravity while moving on a 8.84m radius circle, so we must do:

Answer:
East component is: 18.64 m/s
Explanation:
If the resultant is 32.5 m/s directed 35 degrees east of north, then we use the sin(35) projection to find the east component of the velocity:
East component = 32.5 m/s * sin(35) = 18.64 m/s