Friction worksheet

1. Coefficient of kinetic friction (μk): 1.19

1. Use the gravity value you entered

   $g$$=7.4\text{\hspace{0.17em}m/s²}$

2. Evaluate cos θ for θ = 34°

   $\text{cos}34\text{\hspace{0.17em}°}$$=0.82903757$

3. Find how hard the object presses into the slope (the normal force): mass × gravity × cos of the angle

   $22\times 7.4\times 0.82903757$$=134.967317\text{\hspace{0.17em}N}$

4. Find the coefficient: since friction F = μ × N, divide the friction force by the normal force

   $\frac{160}{134.967317}$$=1.185472$

2. Kinetic friction force: 0.24 kN

1. Multiply the grip number μ by how hard the surfaces press together (N). That gives the kinetic friction force

   $0.4\times 600$$=240\text{\hspace{0.17em}N}$

2. Change the answer to kN, the unit you picked: divide by 1,000

   $\frac{240}{\mathrm{1,000}}$$=0.24\text{\hspace{0.17em}kN}$

3. Normal force: 76.44 lbf

1. Find the normal force: since friction F = μ × N, divide the friction force by the coefficient μ

   $\frac{170}{0.5}$$=340\text{\hspace{0.17em}N}$

2. Change the answer to lbf, the unit you picked: divide by 4.448221615261

   $\frac{340}{4.448221615261}$$=76.435041\text{\hspace{0.17em}lbf}$

4. Normal force: 800 N

1. Find the normal force: since friction F = μ × N, divide the friction force by the coefficient μ

   $\frac{240}{0.3}$$=800\text{\hspace{0.17em}N}$

5. Maximum static friction force: 21.05 lbf

1. Use the gravity value you entered

   $g$$=11\text{\hspace{0.17em}m/s²}$

2. Evaluate cos θ for θ = 38°

   $\text{cos}38\text{\hspace{0.17em}°}$$=0.78801075$

3. Find how hard the object presses into the slope (the normal force): mass × gravity × cos of the angle

   $18\times 11\times 0.78801075$$=156.026129\text{\hspace{0.17em}N}$

4. Multiply the grip number μ by how hard the surfaces press together (N). That gives the maximum static friction force

   $0.6\times 156.026129$$=93.615678\text{\hspace{0.17em}N}$

5. Change the answer to lbf, the unit you picked: divide by 4.448221615261

   $\frac{93.615678}{4.448221615261}$$=21.045642\text{\hspace{0.17em}lbf}$

6. Kinetic friction force: 0.22 kN

1. Multiply the grip number μ by how hard the surfaces press together (N). That gives the kinetic friction force

   $0.4\times 550$$=220\text{\hspace{0.17em}N}$

2. Change the answer to kN, the unit you picked: divide by 1,000

   $\frac{220}{\mathrm{1,000}}$$=0.22\text{\hspace{0.17em}kN}$

7. Kinetic friction force: 7.44 N

1. Use the surface gravity of the Moon

   $g$$=1.62\text{\hspace{0.17em}m/s²}$

2. Evaluate cos θ for θ = 28°

   $\text{cos}28\text{\hspace{0.17em}°}$$=0.88294759$

3. Find how hard the object presses into the slope (the normal force): mass × gravity × cos of the angle

   $13\times 1.62\times 0.88294759$$=18.594876\text{\hspace{0.17em}N}$

4. Multiply the grip number μ by how hard the surfaces press together (N). That gives the kinetic friction force

   $0.4\times 18.594876$$=7.437951\text{\hspace{0.17em}N}$

8. Maximum static friction force: 50.58 lbf

1. Multiply the grip number μ by how hard the surfaces press together (N). That gives the maximum static friction force

   $0.5\times 450$$=225\text{\hspace{0.17em}N}$

2. Change the answer to lbf, the unit you picked: divide by 4.448221615261

   $\frac{225}{4.448221615261}$$=50.582012\text{\hspace{0.17em}lbf}$

9. Normal force: 233.33 N

1. Find the normal force: since friction F = μ × N, divide the friction force by the coefficient μ

   $\frac{140}{0.6}$$=233.333333\text{\hspace{0.17em}N}$

10. Maximum static friction force: 44.96 lbf

1. Multiply the grip number μ by how hard the surfaces press together (N). That gives the maximum static friction force

   $0.5\times 400$$=200\text{\hspace{0.17em}N}$

2. Change the answer to lbf, the unit you picked: divide by 4.448221615261

   $\frac{200}{4.448221615261}$$=44.961789\text{\hspace{0.17em}lbf}$