Agardener pushes a 20 kg lawnmower whose handle is tilted up 37∘ above horizontal. the lawnmower's coefficient of rolling friction is 0.18. how much power does the gardener have to supply to push the lawnmower at a constant speed of 1.5 m/s ? assume his push is parallel to the handle.

58.4 W

Explanation:

The speed of the lawnmower is constant: this means that its acceleration is zero, so the net force on it is zero.

The equation of the forces along the two directions therefore are:

- Perpendicular to the floor:

- Parallel to the floor:

where

F is the push of the gardener

R is the normal reaction

m = 20 kg is the mass

g = 9.8 m/s^2 is the acceleration of gravity

is the coefficient of friction

Solving for R,

Substituting into the other equation,

And the power he must supply therefore is the product of this force and the speed:

28. evolution

29. environment, survive, offspring  

explanation:

  the grams     of oxygen gas   that can be produced     is 20.6   grams of o₂

calculation

2liclo₃ →   2 licl + 3 o₂

step 1:   find the moles of liclo₃

moles = mass÷ molar mass

from periodic table the molar mass of liclo₃ =6.9 +35.5   +(16 x3) =90.4 g/mol

moles=38.7 g÷90.4 g/mol=0.4281   moles

step 2:   use the   mole ratio   to calculate the moles of o2

from equation above, liclo₃: o₂   is 2: 3  

therefore the moles of   o₂=0.4281 moles x3/2 =0.6422   moles

step 3: find mass   of o₂

mass= moles x molar mass

from periodic table the   molar mass of   o₂ = 16 x2= 32 g/mol

mass=0.6422   moles   x   32 g/mol = 20.6 grams of o₂