Physics

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homework 06 – ALENEZI, THAMER – Due: Mar 31 2017, 11:00 pm (Central time) 1

Question 1, chap 6, sect 2. part 1 of 1 10 points

Two blocks are arranged at the ends of a massless string as shown in the figure. The system starts from rest. When the 2.7 kg mass has fallen through 0.42 m, its downward speed is 1.34 m/s. The acceleration of gravity is 9.8 m/s2 .

2.7 kg

4.12 kg

What is the frictional force between the 4.12 kg mass and the table? Answer in units of N.

Question 2, chap 6, sect 2. part 1 of 2 10 points

A block is released from rest on an inclined plane and moves 3.2 m during the next 3.2 s. The acceleration of gravity is 9.8 m/s2 .

9 k g

µk 35◦

What is the magnitude of the acceleration of the block? Answer in units of m/s2.

Question 3, chap 6, sect 2. part 2 of 2 10 points

What is the coefficient of kinetic friction µk

for the incline?

Question 4, chap 6, sect 2. part 1 of 2 10 points

A string is tied to a book and pulled at an angle α as shown in the diagram. The book remains in contact with the table and does not move.

µs

F α

Which choice best describes the free body diagram in the vertical direction for this situ- ation?

1. N = m g − T sin α

2. N = m g + T sin α

3. N = m g

4. N = m g + T cos α

5. N = m g − T cos α

Question 5, chap 6, sect 2. part 2 of 2 10 points

Which forces change when the string is pulled so that the book moves as compared to when the book is stationary?

1. friction

2. tension in the string

3. friction, tension in the string, and gravi- tational

4. gravitational

5. normal, friction, and tension in the string

6. friction and tension in the string

homework 06 – ALENEZI, THAMER – Due: Mar 31 2017, 11:00 pm (Central time) 2

7. normal

8. None of these

9. normal and gravitational

Question 6, chap 6, sect 2. part 1 of 2 10 points

Two blocks are arranged at the ends of a massless cord over a frictionless massless pulley as shown in the figure. Assume the system starts from rest. When the masses have moved a distance of 0.377 m, their speed is 1.26 m/s. The acceleration of gravity is 9.8 m/s2 .

5.8 kg

4.5 kg

What is the coefficient of friction between m2 and the table?

Question 7, chap 6, sect 2. part 2 of 2 10 points

What is the magnitude of the tension in the cord? Answer in units of N.

Question 8, chap 6, sect 2. part 1 of 1 10 points

The magnitude of each force is 285 N, the force on the right is applied at an angle 21◦

and the mass of the block is 15 kg. The coefficient of friction is 0.187. The acceleration of gravity is 9.8 m/s2 .

15 kg

µ = 0.187

285 N

21◦285 N

What is the magnitude of the resulting ac-

celeration? Answer in units of m/s2.

Question 9, chap 6, sect 2. part 1 of 1 10 points

The coefficient of static friction between the 4.36 kg crate and the 21◦ incline is 0.277. The acceleration of gravity is 9.8 m/s2 .

4.36 kg

µk

21◦

What minimum force F must be applied to the crate perpendicular to the incline to pre- vent the crate from sliding down the incline? Answer in units of N.