Page 77 - Physics Coursebook 2015 (A level)

Chapter 4: Forces – vectors and moments
2 A block of mass 1.5 kg is at rest on a rough surface which is inclined at 20° to the horizontal as shown in Figure 4.28.
20°
Figure 4.28 For End-of-chapter Question 2.
a Draw a free-body diagram showing the three forces acting on the block. [2]
b Calculate the component of the weight that acts down the slope. [2]
c Use your answer to b to determine the force of friction that acts on the block. [2]
d Determine the normal contact force between the block and the surface. [3]
3 The free-body diagram (Figure 4.29) shows three forces that act on a stone hanging at rest from two strings.
tension in string 1 1.00 N 60°
horizontal
Figure 4.29 For End-of-chapter Question 3.
a Calculate the horizontal component of the tension in each string. Why should these two components
be equal in magnitude? [5]
b Calculate the vertical component of the tension in each string. [4]
c Use your answer to b to calculate the weight of the stone. [2]
d Draw a vector diagram of the forces on the stone. This should be a triangle of forces. [1]
e Use your diagram in d to calculate the weight of the stone. [2]
30°
weight of stone
tension in string 2 0.58 N
4 The force F shown in Figure 4.30 has a moment of 40 N m about the pivot. Calculate the magnitude of the force F.
2.0 m
45°
F
Figure 4.30 For End-of-chapter Question 4.
[4]
65