Answer:
A light emitting diode (a semiconductor diode which glows when voltage is applied.
Answer:
The two skaters will move with a common speed of 1.19 m/s.
Explanation:
Given that,
Mass of Alex, 
Initial velocity of Alex, 
Mass of Barbara, 
Initial velocity of Barbara, 
After the collision, the two skaters move together at a common velocity. Let V is the common velocity. Using the conservation of momentum as :

Magnitude of final velocity:

So, the two skaters will move with a common speed of 1.19 m/s.
The clock is pulling the force towards earth's center because of gravity.
That force is equal to:
F = m*g where g is gravitational acceleration.
We will take that g = 9.81m/s^2
Now:
F = 0.25 * 9.81 = 2.4525 N
The string needs to sustain that force, therefore minimum Force that string has to be able to sustain is:
2.4525 N
The total force applied by the three people is:

This force is pushing toward the direction of the motion, while the frictional force

points in the opposite direction.
We can write Newton's second law applied to the block: the resultant of the two forces must be equal to the product between the block's mass and its acceleration

We know the mass of the block, m=500 kg, and the acceleration,

, so we can find the friction:
Answer:
450N
Explanation:
Given data
Mass m= 75kg
Acceleration= 6m/s^2
From the Newtons first law, F=ma
substitute
F=75*6
F= 450N
Hence the force is 450N