How Much Force is Needed to Climb a Hill at Constant Speed with Air Resistance?

[hemetite]

Homework Statement

A bicyclist of mass 65kg (including the bicycle) can coast down a 6 degree hill at steady speed of 6km/h because of air resistance. How much force must be applied to climb the hill at the same speed and same air resistance?

The Attempt at a Solution

since it is at constant speed. the net force is zero.

therefore the

Fg (force due to mg) - Fr (air resistance force) = 0

(mg sin 6) - Fr = 0

Fr= mg sin 6 = 66.58N.

For it to climb back the hill at the same speed and same air restance?

the bicyclist have to tackle the two same force now = 66.58 + mg sin 6 = 133N.

The model answer given is 130N...but i got 133N...

any mistake i have made?

 

[Hootenanny]

Homework Statement

A bicyclist of mass 65kg (including the bicycle) can coast down a 6 degree hill at steady speed of 6km/h because of air resistance. How much force must be applied to climb the hill at the same speed and same air resistance?

The Attempt at a Solution

since it is at constant speed. the net force is zero.

therefore the

Fg (force due to mg) - Fr (air resistance force) = 0

(mg sin 6) - Fr = 0

Fr= mg sin 6 = 66.58N.

For it to climb back the hill at the same speed and same air restance?

the bicyclist have to tackle the two same force now = 66.58 + mg sin 6 = 133N.

The model answer given is 130N...but i got 133N...

any mistake i have made?

You haven't made any mistakes, perhaps the model answer has rounded to 2sf?