A large crate filled with physics laboratory equipment must be moved up an incline onto a truck.
1. The crate is at rest on the incline. What can you say about the force of friction acting on the crate?
a. The friction force point up the include
b. The friction force point down the include
c. the firction force is 0
2. A physicist attempts to push the crate up the incline. The physicist senses that if he applies slightly more force the crate will move up the incline but cannot muster enough strength to get the motion started. What can you say now about the force of friction acting on the crate?
a. The friction force point up the include
b. The friction force point down the include
c. the firction force is 0
3. he first physicist gets a second physicist to help. They both push on the crate, parallel to the surface of the incline, and it moves at constant speed up the incline. How does the force exerted by the two physicists on the crate compare with the force of friction on the crate?
1.a (static friction is pushing up on the box to keep it from sliding down the incline)
2.b (static friction is pushing down on the box to keep him from moving it up the incline)
^^friction always pushes the opposite direction of the force acting on the object^^
3.Fphysisist > Ffriction (they must push with a greater force than friction otherwise the box would stay stationary)
1. c. The friction force is 0. Since the crate is at rest, there is no need for a friction force to oppose its motion.
2. a. The friction force points up the incline. The fact that the physicist senses that the crate will move up the incline with slightly more force indicates that the force of friction is acting to oppose the motion and prevent it from starting.
3. The force exerted by the two physicists on the crate is equal to the force of friction on the crate. Since the crate is moving at a constant speed, the force the physicists apply must match the force of friction to overcome it and maintain the constant speed.
1. The correct answer is b. The friction force points down the incline. Since the crate is at rest, the friction force must be equal in magnitude and opposite in direction to the force pushing the crate down the incline.
2. The correct answer is a. The friction force points up the incline. If the physicist senses that applying slightly more force will get the motion started, it means that the force of friction acting on the crate is in the opposite direction to his applied force. Therefore, he needs to exert a force greater than the force of friction to move the crate up the incline.
3. The force exerted by the two physicists on the crate is equal in magnitude to the force of friction on the crate. Since the crate is moving at a constant speed up the incline, it means that the force exerted by the physicists balances out the force of friction. This is known as the equilibrium condition, where the net force on an object is zero in order to maintain constant velocity.
1. To determine the force of friction acting on the crate, we need to consider the forces acting on it. Since the crate is at rest on the incline, there are two main forces acting on it: the force of gravity (acting vertically downwards) and the normal force (acting perpendicular to the incline). The force of friction is parallel to the incline (along the surface of the incline) and opposes the motion of the crate. In this case, since the crate is at rest, the force of friction must be equal in magnitude and opposite in direction to the component of the force of gravity parallel to the incline. This means that the force of friction points up the incline, so the answer is (a) The friction force points up the incline.
2. In this situation, the physicist is trying to push the crate up the incline but cannot start its motion. This indicates that the force of friction acting on the crate is greater than the force the physicist is applying. If the crate were to move up the incline, the force of friction would need to be overcome by a greater force. Therefore, the force of friction must be pointing down the incline, opposing the motion, and preventing it from starting. The answer is (b) The friction force points down the incline.
3. When both physicists push on the crate parallel to the surface of the incline, they are exerting a force on the crate that helps overcome the force of friction and keep the crate moving at a constant speed up the incline. According to Newton's third law, the force exerted by the two physicists on the crate must be equal in magnitude and opposite in direction to the force of friction. This means that the force exerted by the two physicists on the crate is equal to the force of friction on the crate. So, the force exerted by the two physicists on the crate is equal to the force of friction.