When the ball reaches its original position, it will have the same speed (but would be traveling in the opposite direction). So the average speed is
regardless of how long the ball was in the air.
Answer:
Explanation:
First, the box goes from position x=0 to x=x1, so, the work made by the friction is calculated as:
where is the force of friction, the displacement, m the mass, V is the speed in rest and the initial speed.
V is equal to zero, so:
it means that the force of friction is equal to:
On the other hand, when the box goes from position x=x1 to x=x2, the work-energy theorem said that:
Where is the work done by the person.
Then, solving for :
Finally, replacing by , we get:
Answer:
If the present earth is squeezed to the size of moon, the acceleration due to gravity will be increased by about 14 times since, acceleration due to gravity is inversely proportional to the square of radius if mass is constant.
Answer:
Explanation:
There are two forces acting on the oil drop:
- The force of gravity, downward, given by
where m is the mass of the drop and g is the acceleration due to gravity
- The electric force, upward, given by
where q is the charge of the oil drop and E is the magnitude of the electric field
The oil drop remains stationary, so the two forces are balanced:
where
Substituting into the previous equation and solving for q, we find the charge of the oil drop: