Question

consider a cart being pulled across a frictionless surface at constant speed using force applied at angle theta 0 above horizontal. which is true and why

NF is equal to weight of box

pulling is less than friction force

NF is less than weight of box

Pulling force is equal to friction force

NF is larger than weight of box

Answer 1

Using the Newtons second law

Along y axis , since force is acting at an angle (theta )

mg = Fsin(theta ) + N

N is the normal reaction force

Along x axis

Since constant speed is acting so Acceleration = 0

Fcos(theta ) is the initial force acting on block

a) NF is equal to weight of box - false

Reason : from the above equation ,

N = mg - Fsin(theta), so N is less than mg (weight)

pulling is less than friction force : False

Because there is no frictional force acting , since frictionless surface

NF is less than weight of box : true

Reason : from the equation

N = mg - Fsin(theta), N is less than weight

Pulling force is equal to friction force : False

reason : since it is a frictionless surface, frictional force acting is zero

NF is larger than weight of box : false

Reason : from the equation :

N = mg -Fcos(theta) so N is less than weight