Static Friction
Kinetic Friction
Kinetic / Static Combo
Tension / Free Body Diagrams
Dynamics / Kinematics Basics
100
If an applied force is less than the static force of friction, the acceleration will be
What is zero.
100
A brick is sliding to the right on a horizontal surface. What are the directions of the two surface forces: the friction force and the applied force?
What is left and right
100
(Definition) Friction that acts on an object that is already in motion is called _______.
What is kinetic friction
100
A lamp that has a mass of 80 kg (big lamp) is hanging from a rope attached to the ceiling. What does the free body diagram look like?
^ || || O || || v
100
A physics student pushed a 50kg load across the floor, accelerating it at a rate of 1.5 m/s^2. How much force did she apply?
What is F=75N
200
When the applied force is less than the force of static friction, the force of friction will have the same ________ as the the applied force, in the opposite direction.
What is magnitude.
200
A 10.0 kg brick is sliding on a surface. The coefficient of kinetic friction between the two surfaces is 0.25. What is the size of the force of friction?
What is Fk = (0.25)(10)(9.8) = 24.5 N
200
(Definition) The frictional force between two surfaces that are not moving along each other. It keeps objects from moving when a force is first applied.
What is Static Friction
200
A crane if lifting a box with a mass of 100 kg up with a constant velocity. What is the tension in the cable of the crane?
What is FT = 980 N
200
What average net force is required to accelerate a 9.5 bullet from rest to 650 m/s over a distance of 0.85 along the barrel of a rifle?
What is F = 2361N, a = 248529.41 m/s^2
300
An object has a mass of 50 kg. It has a static friction coefficient of 0.8. What is the static force of friction?
What is Fs = (0.8)(50kg)(9.8m/s^2) = 392 N
300
A 23 kg crate is being pushed across a warehouse floor. The coefficient of kinetic friction between the crate and the floor is 0.7. What is the size of the force of friction.
What is Fk = (23 kg)(0.7)(9.8) = 157.78 N
300
A stationary 15 kg object is located on a table near the surface of the Earth. The coefficient of static friction between the surfaces is 0.40 and of the kinetic friction is 0.3. A horizontal force of 30 N is applied to the object. Draw a free body diagram with forces to scale.
See teacher for answer on white board.
300
An 85 kg mountain climber is repelling down the side of a mountain with an acceleration 3 m/s^2. What is the tension in the rope?
What is Ft = m(a+g) = 85(-3+9.8) = 578N
300
A 10,000 N net force is accelerating a car at a rate of 5.5 m/s^2. What is the cars mass?
What is m = 1818 kg
400
An object has a mass of 50 kg. It's force of static friction is 250N. What is its coefficient of static friction?
What is Us = Fs/Fn Us = 250 N / (50kg * 9.8 m/s^2) Us = 0.04
400

A 50 kg crate is pushed across a warehouse floor with a force of  friction of 100 N. What is the coefficient of friction between the floor and the crate?

What is 0.2

400
A stationary 15 kg object is located on a table near the surface of the Earth. The coefficient of static friction between the surfaces is 0.40 and of the kinetic friction is 0.3. A horizontal force of 45 N is applied to the object. Determine the force of friction.
What is F = 45 N. The object does not move because the applied force is less than the force of static friction.
400
If the tension in a rope is 450N and the acceleration of the object attached to the rope is -2 m/s^2, what is the mass of the object?
What is F=m(a+g), so m = F / (a+g), 450 / (-2+9.8) = 57.7kg
400
A woman weighs 580N. What is her mass?
What is m=59.2 kg
500
Find the mass of an object that has a force of static friction of 300 N and a coefficient of 0.03.
What is m = 1020.4 kg
500

A stationary 15 kg object is located on a table surface of the Earth. The coefficient of kinetic friction between the two surfaces is 0.3. A horizontal force of 100N is applied to the object a) Draw a free body diagram b) Determine the force of friction c) Determine the acceleration of the object

What is a) See board b) 44.1 N c) 3.73 m/s^2

500
A stationary 15 kg object is located on a table near the surface of the Earth. The coefficient of static friction between the surfaces is 0.40 and of the kinetic friction is 0.3. A horizontal force of 60 N is applied to the object. Determine the acceleration of the object.
What is 1.06 m/s^2
500

What does a FBD look like for a car moving at constant velocity?

See teacher for answer

500
A net force of 3000 N is accelerating a 1200 kg elevator upward. If the elevator starts from rest, how long will it take to travel up 15m?
What is a = 2.5 m/s^2, t = 3.46s (must use 2nd kinematics equation)
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