Home / Topics / Newton's Laws & Forces
Friction on inclines with applied force
Intermediate
Include friction direction opposing impending motion.
Pushing a block up a slope, friction points down the slope; pushing it down, friction acts up the slope. Write along-slope balance: F = mg sinθ ± μmg cosθ.
To push a 10 kg block at constant speed up a 30° slope with μ = 0.2: F = 49 + 17 = 66 N.
The sign of friction depends on the direction of motion or tendency.
In more detail
When an applied force pushes at an angle on an object on a slope, the normal force and friction both change. The key step is resolving the applied force into components before applying Newton's laws.
Real-world uses
- Pushing a crate up a ramp uses this analysis to estimate the force required.
- Warehouse conveyors and loading ramps are designed using these calculations.
- Pulling a sled up a hill requires you to include the friction force acting down the slope, which opposes the sled's motion.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
Does pushing down increase the friction?
Yes. A downward component of the push increases the normal force, which increases the maximum friction.
Which direction does friction act?
Opposite to the direction of motion or the tendency to move.
Which way does friction act on a moving object?
Friction opposes the motion relative to the surface, so it acts in the direction that resists sliding.
Related topics in Newton's Laws & Forces
Kinetic friction · Angle of friction and repose · Rolling friction · Block on block problems · Impulse · Linear momentum