Coefficient of Friction

 What is the unit called that measures force?

• weight
• meter
• Newton
• kilogram

What direction does friction act relative to motion?

• in the same direction
• in the opposite direction 
• need more information
• depends on the force

What type of friction is not moving?

• static
• sliding
• fluid
• rolling

Rougher surfaces have ...

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

A box takes 40 N to start moving when the coefficient of static friction is .54. What is the weight of the box? 

• 81 N
• 18 N
• 98 N
• 74 N

When looking at friction problems, if the net force in the x-direction on an object is zero, what can we say about its acceleration?

• it is positive

• it is negative

• it is zero

• not enough information is given

Choose the best procedure to measure the force of static friction.

• Using a spring scale record the amount of force it takes to keep a block in motion.

• Using a spring scale record the amount of force it takes to budge a stationary block.

• Derive the formula found on the formula chart, then using a calculator, multiply mass by acceleration of the bock.

• Using a triple beam balance, find the weight of the object, this will also tell you the force.

A hockey puck slides on ice at a constant velocity. What is the net force acting on the puck?

• Zero
• Equal to its weight
• Less than its weight but greater than zero
• Depends on the speed of the puck

If the mass of the block is 20.0 kg, what is the magnitude of F_grav?

• 170 N

• 98.1 N

• 196 N

• 20.0 kg

Name the missing force...

• applied force
• weight force
• lift
• normal force