Question

Assignment 3 (Work, Energy and

Momentum) – Due Wednesday 20 May 2020

Question 1 (9 marks):

A block of mass 2.5 kg is pushed 2.2 m along a frictionless horizontal table by a

constant 16 N force directed 25° downward to the horizontal. Determine the work

done on the block by:

a) The applied force (3)

b) The normal force exerted by the table, and (2)

c) The gravitational force (2)

d) Determine the total work done (2)

25°

2.5 kg

Answer 1

Given data

Mass of block m= 2.5 kg

Acceleration due to gravity g= 9.80 m/s²

Applied force is F= 16 N

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a)

The work done by the applied force is

$W_F=Fd cos25^o=(16 N)(2.2 m) cos25=31.9 N= 32 J$

b)

The work done by the normal force exerted by the table, is

$W_N= Nd cos90^o=Nd(0) = 0 J$

c)

The work done by the gravitational force is

$W_G= F_Gd cos90^o=F_Gd = 0 J$

d)

The total work done is

$W_Total= W_F+W_N+ W_G= 32 J$