Answer: The correct answer would be C. Salt crystals are hard and brittle because they are made up of atoms that combine by ionic bonding.
Explanation: All the other ones are chemical changes because a new substance is formed.
Answer:
a) No difference
Explanation:
Since the billiard balls are identical , they have the same mass. Also they have the same speed
Since the angular momentum is conserved and the total energy is conserved ( if we assume elastic collision)
1/2 m1 * v i1² +1/2 m2 * v i1² = 1/2 m1 * v f1² +1/2 m2 * v f2²
where m= mass , vi= initial velocity , vf= final velocity
since m1=m2=m , vi1=vi2=vi
1/2 m1 * v i1² +1/2 m2 * v i1² = 1/2 m1 * v f1² +1/2 m2 * v f2²
m * v i² = 1/2 m (v f1² +v f2² )
vi² = 1/2(v f1² +v f2² )
since the 2 balls are indistinguishable from each other (they have identical initial mass and velocity) there is no reason for a preferential speed for one of the balls and therefore its velocities must be equal . Thus vf1=vf2=vf
therefore
v i² = 1/2(v f1² +v f2² ) = v i1² = 1/2* 2vf² = vf²
and thus
vi= vf
in conclusion, there is no difference in speed after the rebound
Answer:
14.5 hours
Explanation:
The relationship between speed, time and distance for a uniform motion is

where
v is the speed
d is the distance
t is the time taken
Here we know:
v = 24.0 m/s is the average speed
is the distance
Solving the equation, we find the time taken:

And since
1 hour = 3600 s
The time in hours is

The frequency of the wheel is given by:

where N is the number of revolutions and t is the time taken. By using N=100 and t=10 s, we find the frequency of the wheel:

And now we can find the angular speed of the wheel, which is related to the frequency by:
Without friction, the amount of work only depends on the final height,
and is not affected by the route used to get there.
If the ramp has no friction, then it has no effect on the total amount
of work done. The work to lift the load straight up is the same.
If the ramp has some friction, then it takes more work to use the ramp
than to lift the load straight up. Then the work to lift the load straight up
would be less than when the ramp is used.