Answer:
4086 J
Explanation:
The potential energy is transformed to kinetic energy less the frictional energy. Potential energy= mgh where m represent mass, g is acceleration due to gravity and h is the height of cliff
Since we have force of air resistance, work done due to air resistance will be product of force and distance
Substituting 10 Kg for m, 9.81 for g and 60 m for F then the kinetic energy at the bottom will be
KE= 10*9.81*60- (30*60)=4086 J
Efficiency = useful energy out / total energy in x 100
= 100/400 x 100
=0.25 x 100
= 25%
25%
Answer:
The resistance is 
Explanation:
Given that,
Diameter of tube = 8.5 mm
Length = 8 cm
Resistivity = 2.5 m
We need to calculate the resistance
The resistance is equal to the product of the resistivity and length divided by the area of cross section .
In mathematical form,
Where, 
=resistivity
l = length
A = area of cross section
Put the value into the formula
Hence, The resistance is
Answer:
32000 N
Explanation:
From the question given above, the following data were obtained:
Initial velocity (u) = 40 m/s
Distance (s) = 10 m
Final velocity (v) = 0 m/s
Mass (m) of car = 400 Kg
Force (F) =?
Next, we shall determine the acceleration of the the car. This can be obtained as follow:
Initial velocity (u) = 40 m/s
Distance (s) = 10 m
Final velocity (v) = 0 m/s
Acceleration (a) =?
v² = u² + 2as
0² = 40² + (2 × a × 10)
0 = 1600 + 20a
Collect like terms
0 – 1600 = 20a
–1600 = 20a
Divide both side by –1600
a = –1600 / 20
a = –80 m/s²
The negative sign indicate that the car is decelerating i.e coming to rest.
Finally, we shall determine the force needed to stop the car. This can be obtained as follow:
Mass (m) of car = 400 Kg
Acceleration (a) = –80 m/s²
Force (F) =?
F = ma
F = 400 × –80
F = – 32000 N
NOTE: The negative sign indicate that the force is in opposite direction to the motion of the car.
