Question

A block of mass 50 kg is to be accelerated at 3 m/s2 along the

horizontal surface as shown in Figure Q7(a). The coefficient of
kinetic friction between the surfaces is 0.7.
(i) Sketch a free body diagram. (3)
(ii) Determine the magnitude of the required force P. (5)

Answer 1

(i) The free body diagram of the forces acting on the block of mass in the image attached.

(ii) The magnitude if the required force is 493 N.

How to draw the free body diagram and calculate the required force?

(i) The free body diagram of the forces acting on the block of mass include the following;

force of friction acting leftwards (Fs)

the required force acting rightwards (F)

weight of the block acting downwards (W)

normal force of the ground acting upwards (N)

(ii) The magnitude if the required force is calculated by applying the following formula as follows;

F(net) = ma

F - Fs = ma

where;

• F is the required force
• Fs is the force of friction
• m is the mass
• a is the acceleration

F - μmg = ma

F = ma + μmg

F = m(a + μg)

F = 50(3 + 0.7 x 9.8)

F = 493 N