Chemical equilibrium

Grade 12 practice questions


2.1. A person pushes a lawnmower of mass 15 kg at a constant speed in a straight line over a flat grass surface with a force of 90 N. The force is directed along the handle of the lawnmower. The handle has been set at an angle of 40° to the horizontal. Refer to the diagram below. 
2.1.1 Draw a labelled free-body diagram for the lawnmower.  (4)

2.1.2. Why is it CORRECT to say that the moving lawnmower is in equilibrium?  (1) 
2.1.3. Calculate the magnitude of the frictional force acting between the
lawnmower and the grass  (3) 

The lawnmower is now brought to a stop. 
2.1.4. Calculate the magnitude of the constant force that must be applied through the handle in order to accelerate the lawnmower from rest to 2 m∙s-1 in a time of 3 s. Assume that the frictional force between the lawnmower and grass remains the same as in QUESTION 2.1.3. (6)

2.2. Planet Y has a radius of 6 x 10^5 m. A 10 kg mass weighs 20 N on the surface of planet Y
Calculate the mass of planet Y.  (4)



A 5 kg block, resting on a rough horizontal table, is connected by a light inextensible string passing over a light frictionless pulley to another block of mass 2 kg. The 2 kg block hangs vertically as shown in the diagram below

A force of 60 N is applied to the 5 kg block at an angle of 10o to the horizontal, causing the block to accelerate to the left.
The coefficient of kinetic friction between the 5 kg block and the surface of the table is 0,5. Ignore the effects of air friction.

1. Draw a labelled free-body diagram showing ALL the forces acting on the 5 kg block. (5)

2. Calculate the magnitude of the:

2.1. Vertical component of the 60 N force (2)
2.2.Horizontal component of the 60 N force (2)
2.3. State Newton’s Second Law of Motion in words. (2)

3. Calculate the magnitude of the:

3.1.Normal force acting on the 5 kg block (2)
3.2.Tension in the string connecting the two blocks (7)