03c - Frictional Forces

What are the 2 types of friction discussed in the book?

• Static and Dynamic Friction
• Kinetic and Static Friction
• Kinetic and Dynamic Friction
• Dynamic and Moving Friction

What are 2 factors that determine the amount of friction between 2 objects?

• Force and roughness between surfaces
• hills and valleys and how smooth or rough the surface is
• Amount of force and amount of surface the comes in contact
• The force and the weight exerted on the surfaces

Which of the following is opposed by kinetic friction?

• A truck being pushed but not moving
• A box being pushed but not moving
• A box being pushed and sliding across the floor
• A wagon being pulled but not moving

Which of the following is an example of friction that is helpful?

• Brakes used on a bike
• Tires from a car on the road
• Tread on the bottom of your shoes
• All are examples that are helpful

Which of the following is an example of friction that is harmful?

• Pencil marking on paper
• Engine parts wearing out
• sand placed on ice in the winter
• Using an eraser to erase marks

Which would NOT be a way of reducing friction?

• making the surfaces smoother
• using lubricants such as waxes, oils, or grease
• changing from sliding friction to rolling friction using ball bearings
• Using kitty litter on snow and ice to help your car gain traction

The amount of friction depends on the normal force of the objects pressing together.

• True

• False

F_N=100N, F_f=20N

• μ=5.0

• μ=0.2

• μ=1.2

• μ=0.1

Tags

NGSS.HS-PS2-1

Rougher surfaces have ...

• greater friction
• less friction
• the same level of friction

What is the coefficient of static friction if it takes 44 N of force to move a box that weighs 86 N? 

• 0.78
• 0.51
• 0.78 N
• 0.58 N

Tags

NGSS.HS-PS2-1