Skip to main content
Login to unlock Email share
Why does it take more force to start a sled then it does to keep one in motion?
Static Friction: Static friction is the force that opposes the start of motion. When the force applied to the object is greater then the static friction, the object begins to move.
Kinetic friction: Occurs after the start of motion, kinetic friction is less that static.
Snow has little friction because it has few irregularities. As the sled goes over the surface since it has few irregularities it is able to slide faster.
When an object is stationary the irregularities from the snow and the sled have time to stick together, so motion is harder to obtain (N1L, inertia). While in motion the sled is not in any one place for a certain amount of time, therefore the irregularities have less time to stick together.
"An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and direction unless acted upon by an unbalanced force."
Inertia- The resistance an object has to change in its state of motion
The Sum up:
It takes more force to start the sled for two reasons; one is because an object at rest tends to stay at rest. Therefore the sled is resisting the change in movement, instead of keeping in motion. The second reason is that while it is in motion the sled has less time for it's and the snow's irregularities to stick together, therefore sliding faster
Physics Classwork: pg 72, 102
Sum of the forces
Types of friction: