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
To answer these questions, we need to understand the concepts of friction and forces involved.
Question 1:
When you push a block up a ramp with friction, and the block is moving at a constant speed, it means that the forces acting on the block are balanced. In this case, the force you apply (pushing force) is equal to the force of kinetic friction. Therefore, the answer is C) The force you push with is equal to the force of kinetic friction.
To determine this answer, you can use Newton's second law of motion, which states that the net force acting on an object is equal to the mass of the object multiplied by its acceleration. In this case, since the block is moving at a constant speed, its acceleration is zero. Therefore, the net force must also be zero, which means the force you push with is equal to the force of kinetic friction.
Question 2:
When a block is at rest on a table and you start to push on it parallel to the table top, the force of friction initially acts in the opposite direction to your applied force. As you increase your applied force, the force of friction also increases until it reaches its maximum possible value (static friction). Once your applied force exceeds the force of static friction, the block will start moving, and the force of friction will transition from static friction to kinetic friction.
Therefore, the answer is B) The force of friction increases as your force increases until it reaches its maximum possible value, and then the block moves.
To determine this answer, you can apply the concept of static and kinetic friction. Static friction is the force that opposes the initiation of motion, while kinetic friction is the force that opposes the motion of objects already in motion. Initially, when the block is at rest, the force of friction is the maximum static friction. As you increase your applied force, the static friction increases to match your applied force until it reaches its maximum possible value. Once this maximum static friction is exceeded, the block will start to move and transition to kinetic friction.