Answer:
The crate's coefficient of kinetic friction on the floor is 0.23.
Explanation:
Given that,
Mass of the crate, m = 300 kg
One worker pushes forward on the crate with a force of 390 N while the other pulls in the same direction with a force of 320 N using a rope connected to the crate.
The crate slides with a constant speed. It means that the net force acting on it is 0. Net force acting on it is given by :
So, the crate's coefficient of kinetic friction on the floor is 0.23.
Answer:
Because there is no air resistance
Explanation:
When an object falls on Earth, there are essentially two forces acting on it:
- The force of gravity, downward, equal to the weight of the object:
where m is the mass and g the acceleration due to gravity
- The air resistance, F, which acts upward, and whose magnitude is generally proportional to v, the speed of the object
When the object starts its fall, its initial speed is zero: v = 0, so the air resistance is also zero: F=0, and the object accelerates downward due to gravity.
However, as it accelerates downward, its speed increases, and so does the air resistance F. However, F is upward, opposite to the direction of motion, therefore it reduces the net acceleration of the object; at a certain point, the magnitude of the air resistance will become equal to the weight, so that
mg = F
and at that point, the net acceleration of the object will become zero: this means that the object will continue its fall at a constant velocity, called terminal velocity.
On the Moon instead, there is no air resistance: this means that for an object falling down, the speed keeps increasing due to the effect of gravity, and it will never reach a terminal value: therefore, the final velocity at the impact will be much higher than on the Earth, if we assume the two objects have been dropped from a very high altitude from the surface.