The friction force that prevents a stationary object from beginning to slide when an external force is applied, adjusting in magnitude up to a maximum.
It takes more force to get something moving than to keep it moving.
Showing a random 20 of 50 problems.
Example 1
hard
A 20 kg block sits on level ground, μs=0.5, g=10 m/s2. A rope pulls at θ above horizontal. Find the angle that minimizes the pulling force needed to set it in motion.
Example 2
medium
A 5 kg block on a 30∘ incline, μs=0.4, g=10 m/s2. Find the friction force needed to keep it static, and whether it actually does. (sin30∘=0.5, cos30∘=0.866.)
Example 3
medium
A 2 kg block sits on a board. The board is tilted slowly. Slipping begins at θ=18∘. Find μs.
Example 4
hard
Two blocks A (2 kg, top) and B (3 kg, bottom) sit stacked on a frictionless floor. Between them μs=0.4. A horizontal force F is applied to B. Find the largest F for which A does not slide. (g=10 m/s2.)
Example 5
medium
A 2 kg book is pressed against a vertical wall by a horizontal force N=50N. If μs=0.5, g=10m/s2, will it stay (not slide down)?
Example 6
challenge
A 4 kg block rests on a 30∘ incline with μs=0.3, g=10m/s2 (sin30∘=0.5, cos30∘=0.866). It does not stay by friction alone. Find the minimum force along the incline (up-slope) to hold it static.
Example 7
easy
A 10 kg block on a level floor has μs=0.4, g=10 m/s2. A force of 35 N is applied horizontally. Find the static friction.
Example 8
hard
A 2 kg block sits on top of a 3 kg block; both on a frictionless floor. The contact coefficient is μs=0.2, g=10 m/s2. A horizontal force is applied to the top block. Find the largest force without slipping.
Example 9
medium
A car on a flat road accelerates from rest by static friction with the road. If μs=0.7 and g=10 m/s2, find the maximum acceleration.
Example 10
medium
A block needs at least 12N to start moving and only 8N to keep moving at constant speed, with N=40N. Find μs and μk.
Example 11
medium
A 10 kg block on a 20∘ incline, μs=0.5, g=10m/s2 (sin20∘=0.342, cos20∘=0.940). Does it stay at rest?
Example 12
hard
A car rounds a flat curve of radius 50 m. μs=0.6, g=10 m/s2. Find the maximum speed without slipping.
Example 13
medium
A 6 kg block on level ground with μs=0.3, g=10 m/s2. A rope pulls at θ=37∘ above horizontal with F=25 N. Does the block move? (sin37∘=0.6, cos37∘=0.8.)
Example 14
easy
A 5 kg block on a level surface barely slips when pushed with 30 N. Find μs. (g=10 m/s2.)
Example 15
medium
On a level surface, max static friction on a block is 14 N, kinetic friction is 10 N. A constant 12 N push is applied. Does the block accelerate?
Example 16
medium
On a flat bed of a truck, a 5kg crate has μs=0.4, g=10m/s2. What maximum acceleration can the truck have without the crate sliding?
Example 17
challenge
A car on a banked curve of radius 80 m, banking angle 20∘, μs=0.3, g=10 m/s2 (sin=0.342, cos=0.940). Find the maximum speed without slipping.
Example 18
easy
A horizontal push of 8 N is applied to a 4 kg block on level ground. If μs=0.3 and g=10 m/s2, find the static friction.
Example 19
easy
Why is it generally harder to start a heavy box moving than to keep it sliding?
Example 20
easy
A resting crate has maximum static friction 50N. A worker pushes with 30N. What friction force acts on the crate?