True or Force
Friction always acts opposite the direction of motion.
True
a mass dangles by a spring
Fe and Fg are balanced. One arrow in each direction.
This value describes how rough two interacting surfaces are.
the coefficient of friction
A 0.2 kg puck sits against a spring k = 200 N/m compressed 0.10 m on a frictionless surface. What is its initial acceleration (m/s²)?
100m/s2
Doubling the normal force has what effect on the force of kinetic friction (μₖ constant)
doubles it
The normal force always equals mg.
False. On level ground with no vertical forces added.
A puck slides across a sheet
of frictionless ice at a constant velocity
balanced forces up and down. No forces horizontally
A 1.5 kg blueberry bran muffin slides across the floor. If µ = 0.35, what is the force of friction on the muffin?
5.2N
A 12.0 kg box is placed on a 25° incline. There is no friction.
What is the acceleration of the box down the incline?
4.1 m/s²
What will be the normal force if I push a 10.0kg block down with 100N of force?
198N
If you double the stretch of a spring, you double the force required.
True
A mass on an incline (include friction)
gravity straight down, normal force perpendicular to incline, friction opposed to motion
While Wii bowling, Ms W notices that the 4.0 kg ball slows from 18 m/s to 16 m/s in 4.0 s. What is the force of friction on the ball?
2.0N
A student compresses a spring-loaded launcher by 0.30 m.
The spring constant of the launcher is 40 N/m, and the mass of the object being launched is 0.20 kg.
What is the initial acceleration of the object when released?
60 m/s²
On a frictionless incline, doubling the mass does this to the acceleration.
no change.
On an incline, the normal force is always equal to the object’s weight.
False. On an incline, the normal force is less than the object’s weight and equals mgcosθ
A book is held against the wall
gravity opposes friction, normal force opposes applied force. ALL BALANCED
What is the minimum force required to hold a 9.50 kg box of smaller boxes against a vertical wall if the coefficient of friction is 0.435?
214N
A student pulls a 5.0 kg sled with a rope that makes a 30° angle above the horizontal.
The student applies a force of 40 N along the rope.
What is the horizontal acceleration of the sled?
(Assume no friction.)
6.9 m/s2
A net force of F on a mass m produces an acceleration of 4.0 m/s². What acceleration results from a force of 3F acting on a mass of 2m?
a = (3F)/(2m) = (3/2)(4) = 6 m/s²
If you press down harder on an object, the frictional force can increase.
True. Normal force increases → friction increases
A 0.5 kg cart is held against a horizontal spring compressed by 0.20 m. Draw the FBD for the moment just after the spring is released
elastic force, friction, normal force and gravity. Elastic force greater than friction
A 22.5 kg dog on a skateboard is initially moving at 15 m/s and rolls to a stop in 64 m. Find µ.
0.18
A 4.0 kg block rests on a table connected to a 6.0 kg hanging block. The coefficient of kinetic friction for the block on the table is 0.30. What is the acceleration of the system?
4.7 m/s²
A net force of F applied to a mass m produces an acceleration of 6 m/s².
If the force is quadrupled and the mass is halved, what is the new acceleration?
48 m/s²