1.If a block weighs 30 pounds and has a static friction of .7 and a sliding friction of .55.

a. How much force must be applied to just cause motion?
b. Once motion has begun what force must be maintained to cause constant velocity motion?

2.A plank is tilted slowly to an angle of 30 degrees with a 12 pound block on it
Find FN, FF and the static friction?

3.A force of 26lbs. causes impending motion. If the force is maintained at 26lbs.Fn=Fw=65lbs and the sliding friction is .28.
find:
a.mass of the block
b.FF
c.acceleration
What force must be maintained to cause an acceleration of 2ft/s^2?

This was posted twice. I already did #1. You will get quicker answers if you post one queston at a time.

1. If a block weighs 30 pounds and has a static friction of 0.7 and a sliding friction of 0.55, we can use the following formulas to determine the forces required:

a. To just cause motion, the force must overcome the static friction. The equation to calculate this force is:
Force to overcome static friction = static friction coefficient * normal force

The normal force is equal to the weight of the block. Therefore, the force to just cause motion is:
Force to cause motion = static friction coefficient * weight of the block

Substituting the given values, we have:
Force to cause motion = 0.7 * 30 pounds = 21 pounds

So, a force of 21 pounds must be applied to just cause motion.

b. Once motion has begun, the force required to maintain constant velocity motion is equal to the sliding friction force. It can be calculated using the equation:
Force to maintain constant velocity motion = sliding friction coefficient * normal force

Again, the normal force is equal to the weight of the block. Therefore, the force to maintain constant velocity motion is:
Force to maintain constant velocity motion = sliding friction coefficient * weight of the block

Substituting the given values, we have:
Force to maintain constant velocity motion = 0.55 * 30 pounds = 16.5 pounds

So, a force of 16.5 pounds must be maintained to cause constant velocity motion.

2. If a plank is tilted slowly to an angle of 30 degrees with a 12 pound block on it, we can find the normal force (FN), frictional force (FF), and static friction:

First, we need to find the components of force acting on the block along the tilted plane:
Weight component (Wsinθ) = weight of the block * sin(angle)
Normal force component (Wcosθ) = weight of the block * cos(angle)

The normal force (FN) is equal to the normal force component:
FN = Wcosθ

Substituting the given values, we have:
FN = 12 pounds * cos(30 degrees)
FN ≈ 10.392 pounds

The frictional force (FF) is equal to the static friction coefficient times the normal force:
FF = static friction coefficient * FN

Substituting the given value for the static friction coefficient, we have:
FF = 0.7 * 10.392 pounds
FF ≈ 7.27 pounds

Therefore, the normal force (FN) is approximately 10.392 pounds and the static frictional force (FF) is approximately 7.27 pounds.

3. If a force of 26 pounds causes impending motion and the force is maintained at 26 pounds, FN = Fw = 65 pounds, and the sliding friction coefficient is 0.28, we can find the:

a. Mass of the block:
Using Newton's second law of motion, which states that force = mass * acceleration, we can rearrange the equation to solve for mass:
Mass = force / acceleration

Given that the force is 26 pounds and the acceleration is unknown, we cannot directly calculate the mass. If the acceleration is 0, the mass would be undefined (as division by zero is not possible).

b. Frictional force (FF):
The frictional force (FF) is equal to the sliding friction coefficient times the normal force:
FF = sliding friction coefficient * FN

Substituting the given values, we have:
FF = 0.28 * 65 pounds
FF ≈ 18.2 pounds

Therefore, the frictional force (FF) is approximately 18.2 pounds.

c. Acceleration:
Since the force is maintained at 26 pounds, the force causing acceleration is the difference between the force required for impending motion and the frictional force:
Force for acceleration = force - FF

Substituting the given values, we have:
Force for acceleration = 26 pounds - 18.2 pounds
Force for acceleration ≈ 7.8 pounds

Using the formula force = mass * acceleration, we can rearrange the equation to solve for acceleration:
Acceleration = force / mass

Since the mass is unknown, we cannot directly calculate the acceleration without further information.

To determine the force required to cause an acceleration of 2 ft/s^2, we can rearrange the formula force = mass * acceleration and substitute the given values:
Force = mass * acceleration
Force = mass * 2 ft/s^2

Here again, without knowing the mass, we cannot directly calculate the force required to cause an acceleration of 2 ft/s^2.