physics MC QUESTIONS
posted by emiie on .
1. You push a block up a ramp with friction. The block is moving at constant speed ?
A) The force you push with is greater than the force of kinetic friction.
B) The force you push with is less than the force of kinetic friction.
C) The force you push with is equal to the force of kinetic friction.
D) Kinetic friction is not the important friction in this case, static friction is.
Question # 2
A block is sitting at rest on a table. As I start to push on the block parallel to the table top with increasing force, the force of friction acts as follows ?
A) force of friction decreases as my force increases until it reaches zero and the block moves
B) force of friction increases as my force increases until it reaches its maximum possible value, and then the block moves
C) force of friction is constant as my force increases until my force is greater than the force of friction and the block moves
D) none of the above are true

Easy,
The force you push with is less than the force of kinetic friction. 
what about number two ?

Number two involves a little bit of thinking. If you think about it, you will come to the conclusion that the answer is "None of the above is true".
 David 
thank you :]

ur welcome ?

Are you sure that the force you push is less than? I thought it should be greater?

Q1: A) The force you push with is greater than the force of kinetic friction.
F = F(fr) + m•g•sinα => F > F(fr)
Q2: D) none of the above are true,
F(fr) = k•N = k•m•g 
You people are all fools, the correct answers are the following;
1. A) The force you push with is greater than the force of kinetic friction.
2. B) force of friction increases as my force increases until it reaches its maximum possible value, and then the block moves
Yours truly,
Dr. Phillips
Ph.D