IB A4.3 - Friction

Get the Assessment: FA04.3.docx

The Assessment Solved:

Show your work, round to the correct significant figures, circle your answers, and label them with units. Use the convention that to the right is positive, and to the left is negative.Every force should be labeled "Right" or "Left", and every acceleration should be labeled as "accel" = "acceleration" (speeding up) or "decel" = "deceleration" (slowing down)

A 4.25 kg block of wood has a kinetic coefficient of friction of 0.120 between it and the level floor.

2:01 FA4 3 Part #0 - Finding the force of Friction

1. If the block is sliding to the right, and I exert a force of 7.80 N to the right, what is the acceleration of the block?

(+0.658 m/s/s, accel)

2. If the block is sliding to the left, and I exert a force of 3.50 N to the right, what is the acceleration of the block?

(+2.00 m/s/s, decel)

3. If the block is sliding to the right, and accelerating to the right at 2.35 m/s/s, what must be the outside force acting on the block?

(15.0 N Right)

4. If the block is sliding to the left, but is decelerating at 3.12 m/s/s, what must be the outside force acting on the block?

(8.26 N Right)

5. If the block is initially sliding to the right at 3.50 m/s, and stops in a distance of 1.50 m, what outside force acted on the block as it was stopping?

(12.4 N Left)

More Practice Problems

Get this document: Worksheet-Friction4.3.docx

Use the convention that to the right is positive, and to the left is negative. (every answer should be overtly labeled + or -)

1. There is a coefficient of kinetic friction of 0.140 between a 5.20 kg box and the level floor.

1:37 FA4 3 Ex#1 Part #0

a. If the box is sliding to the left, and we exert a force of 5.50 N to the right, what is the acceleration? 1:56 FA4 3 Ex#1 Part #1

b. If the box is sliding to the right, and we exert a force of 6.90 N to the left, what is the acceleration? 1:43 FA4 3 Ex#1 Part #2

c. The box is sliding to the right, but is decelerating at 3.30 m/s/s, what outside force besides friction is acting on it? 1:59 FA4 3 Ex#1 Part #3

d. If the box is sliding and accelerating to the left at 4.90 m/s/s, what force must be acting on it? 1:41 FA4 3 Ex#1 Part #4

e. The box slides from rest to the right reaching a velocity of 14.5 m/s in a distance of 16.8 m. What outside force was acting? 3:38 FA4 3 Ex#1 Part #5

2. There is a coefficient of kinetic friction of 0.105 between a 4.75 kg block of wood and the level floor.

1:37 Practice 4 3 #2

a. If there is a force of 8.20 N to the right, and the block is sliding to the right, what is the acceleration? 2:03 Practice 4 3 #2a

b. If the block is sliding to the left, and there is a force of 2.70 N to the left, what is the acceleration of the block? 2:14 Practice 4 3 #2b

c. What applied force would make the block accelerate and slide to the right at 4.30 m/s/s? 2:07 Practice 4 3 #2c

d. If the block is sliding to the left, but is decelerating at 7.10 m/s/s, what force must be applied to it? 2:20 Practice 4 3 #2d

e. If you apply 8.90 N to the right and the block starts to slide to the right from rest, what will be the velocity in 8.00 seconds? 2:34 Practice 4 3 #2e

3. There is a coefficient of kinetic friction of 0.310 between an 8.35 kg block of wood and the level floor.

1:55 Practice 4 3 #3

a. If the block is sliding to the right, and there is a force of 13.0 N to the right, what is the acceleration? 1:30 Practice 4 3 #3a

b. If the block is sliding to the right, but there is a force of 12.4 N to the left, what is the acceleration? 1:31 Practice 4 3 #3b

c. If the block is sliding to the left, but is decelerating at 2.80 m/s/s, what outside force must be acting? 2:27 Practice 4 3 #3c

d. If the block is sliding to the right, but is decelerating at 7.36 m/s/s, what is the force acting on the block? 1:55 Practice 4 3 #3d

e. From rest the block reaches a speed of 15.0 m/s from rest in a distance of 20.0 m. What force was acting? 2:26 Practice 4 3 #3e

4. There is a coefficient of kinetic friction of 0.155 between a 3.10 kg block of wood and the level floor.

a. If the block is sliding to the right, and you exert a force of 4.19 N to the left, what is the acceleration?

b. If the block is sliding to the left, and you exert a force of 6.32 N to the left, what is the acceleration?

c. If the block is sliding and accelerating to the right at 4.45 m/s/s, what force must be applied?

d. If the block is sliding to the left and accelerating to the left at 1.75 m/s/s, what force must be applied?

e. The block displaces itself to the left 12.0 m from rest in 2.87 s. What force must have acted?

5. There is a coefficient of kinetic friction of 0.235 between an 8.85 kg box and the level floor.

a. If the box is sliding to the left, and there is a force of 13.5 N to the left, what is the acceleration?

b. If the box is accelerating to the right, and there is a force of 34.7 N to the right, what is the acceleration?

c. If the box is sliding to the right, but is decelerating at 6.50 m/s/s, what force must be acting on the box?

d. If the box is sliding to the left, but is decelerating at 1.29 m/s/s, what must be the force acting on the box?

e. If the box is sliding to the right, and there is a force of 32.0 N to the right, what will be its final velocity from rest when is has gone 45.0 m?

The Instruction for this unit:

Introduction to Friction: