Answer:
First let's find the work.
Work = Force*Displacement
= 20*5
= 100 Joules
Power = Work/Time
= 100/4
= 25 Watts
Explanation :
When a person is sliding with constant velocity, the forces that are acting on him are :
(1) Weight, W = mg where g is acceleration due to gravity.
(2) Friction forces acting opposite to the direction of motion.
(3) Normal force.
The forces acting on the person is balanced because the person is sliding with constant velocity.
From figure it is clear that, friction force is balanced by 
and normal is balanced by 
.
v₀ = initial velocity of the mobile = 10 m/s
v = final velocity of the mobile = 20 m/s
a = acceleration of the mobile = 5 m/s²
d = distance traveled during this operation = ?
Using the kinematics equation
v² = v²₀ + 2 a d
inserting the above values in the equation
20² = 10² + 2 (5) d
400 = 100 + 10 d
subtracting 100 both side
400 - 100 = 100 - 100 + 10 d
300 = 10 d
dividing both side by 10
300/10 = 10 d/10
d = 30 m
hence mobile travels 30 m.
First, we must find the vertical distance traveled upwards by the ball due to the throw. For this, we will use the formula:
2as = v² - u²
Because the final velocity v is 0 in such cases
s = -u²/2a; because both u and a are downwards, the negative sign cancels
s = 14.5² / 2*9.81
s = 10.72 meters
Next, to find the time taken to reach the ground, we need the height above the ground. This is:
45 + 10.72 = 55.72 m
We will use the formula
s = ut + 0.5at²
to find the time taken with the initial velocity u = 0.
55.72 = 0.5 * 9.81 * t²
t = 3.37 seconds
An insulator which is also called a 'dielectric'.
