Answer:
a. 
Explanation:
The equation of the forces along the directions parallel and perpendicular to the slope are:
- Along the parallel direction:
where
:
m = 6.0 kg is the mass of the box
g = 9.8 m/s^2 the acceleration of gravity
is the angle of the slope
is the coefficient of friction
R is the normal reaction
a is the acceleration
- Along the perpendicular direction:
From the 2nd equation, we get an expression for the reaction force:
And substituting into the 1st equation, we can find the acceleration:
Solving for a,
Answer:
b. Static > sliding > rolling friction.
Explanation:
Static friction is greater than sliding friction. It takes more force to get an object to start sliding than to keep it sliding.
Sliding friction is greater than rolling friction. There are fewer points of contact for a round surface compared to a flat one.
Answer:
4400 Joules
73.33 Joules
25.9325 Joules
Explanation:
P = Power = 800 W
t = Time = 22 s
F = Force
r = Radius of arm = 90 cm
Energy

As the efficiency is 25%

Energy used in the race is 4400 Joules
Half of the energy is used in the arm

So, per stroke of paddle

The energy expenditure per arm stroke is 73.33 Joules
Displacement will be the half of the perimeter of the circle

Work done

The average force of the hand on the water is 25.9325 Joules