Solve the following problems using what you know about
Newton’s Laws and the four powerful equations. Be
careful, some of the problems have multiple parts!
1.) d = ½(v +
2.) d = v0t +
3.) v2 =
v02 + 2ad
4.) v = v0 + at
You know these! Remember: forces come in pairs,
no force is acting on a body in a constant state of motion,
and Fnet = ma
1 N = 1 kg · m/s2
Ffr = μFn where μ = coefficient of
μk = coefficient of kinetic friction
μs = coefficient of static friction
Hint: Use meters, kilograms, and
seconds or units derived from these for all
measurements! And answer questions with complete sentences.
- What is the definition of kinetic
- What is the definition of static
- What force does the amount of friction
depend on exclusively?
- Which is greater: static or kinetic friction? Justify your answer using an example from your own experience.
- The coefficient of static friction between a brick and a
concrete floor is 0.5. If the mass of the brick is 2.1 kg, what
force is required to get the brick to slide across the concrete?
- What is the coefficient of kinetic friction if it takes 3.2 N to
keep the 2.1-kg brick moving at a steady speed?
- A force of 30.0 N is required to start a box moving
across a horizontal concrete floor. If the coefficient of static friction (μs) is 0.4, what is the mass of the box?
- A 1,200 kg car skids to a halt in 6.9 s. If the car was
moving at 37 m/s before skidding, calculate:
Is the coefficient you calculated in part c. μk or μs?
- the acceleration of the car
- the frictional force that stopped the car
- the coefficient of friction between the car and the
- The coefficient of kinetic friction between a wooden block with a mass of 0.5 kg and a table-top is 0.4. The coefficient of static friction is 0.5.
- How much force is required to get the block to start sliding across the table?
- How much force is requied to keep it moving at a steady speed?
- How much force is required to accelerate it at 1 m/s2?
- A 2.0-kg piece of steel is placed on top of the wooden block. Repeat the calculations you made above but now for the wooden block with the piece of steel on top of it.
- The coefficient of kinetic friction on an air table is 0.000 001. How much force does it take to keep a 20-g puck moving at a steady speed? How much force is required to accelerate the puck at 1 m/s2?