Are you familiar with any basic calculus? If so, we can just look at this derivative and see what's happening with our units here..

Here it shows that acceleration is the derivative of velocity with respect to time. In other words, we can say that:

We can read that equation as: "acceleration is the change of velocity divided by the change in time (aka the time interval)."
If you're not familiar with calculus, we can use a simple equation of motion:

where:
vf = final velocity
vi = initial velocity
a = acceleration
t = observed time interval
We can rearrange this equation to find:

This is the same exact thing we wrote before!
Answer:
Explanation:
As a ball dropped into a river, its initial velocity is zero and then it is moving under the acceleration due to gravity. That means the acceleration on the ball is in vertically downwards direction which is equal to the acceleration due to gravity that means - 9.8 m/s^2.
When a bullet is fired from a gun straight downwards direction, the acceleration on the bullet is again acceleration due to gravity and it is acting acting downwards. In this case the initial velocity os not zero but acceleration is - 9.8 m/s^2.
Answer:

Explanation:
Assume that the distance travelled initially is d.
In order to stop the block you need some external force which is friction.
If we use the law of energy conservation:

a)
Looking at the formula you can see that the mass doesn't affect the distance travelled, as lng as the initial velocity is constant (Which indicates that the force must be higher to push the block to the same speed) therefore the distance is the same.
b) If the velocity is doubled, then the distance travelled is multiplied by 4, because the distance deppends on the square of the velocity.
Answer:
Explanation:
The tidal current flows to the east at 2.0 m/s and the speed of the kayaker is 3.0 m/s.
Let Vector
is the tidal current velocity as shown in the diagram.
In order to travel straight across the harbor, the vector addition of both the velocities (i.e the resultant velocity,
must be in the north direction.
Let
is the speed of the kayaker having angle \theta measured north of east as shown in the figure.
For the resultant velocity in the north direction, the tail of the vector
and head of the vector
must lie on the north-south line.
Now, for this condition, from the triangle OAB




Hence, the kayaker must paddle in the direction of
in the north of east direction.