Page 15 - Q & A STPM 2022 Physics

Physics Semester 1 STPM Chapter 1 Physical Quantities and Units
1.3 Scalar and Vectors

Section A Multiple-choice Questions
Question 1
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The diagram shows two forces acting on a box.
Exam Tips
Exam Tips
60 N
Resultant force is a single
60° force that is the sum of all the
80 N forces acting on an object.
Semester
1
What is the resultant force acting on the box?
A 41.1 N at 30° above the horizontal.
B 72.1 N at 60° above the horizontal.
C 100 N at 45° above the horizontal.
D 121.7 N at 25° above the horizontal.

Exam Tips
Answer: D Exam Tips
To find the resultant force,
(i) parallelogram method
60 N F
60° 120°

80 N F

Using cosine rule,
2
2
F = 60 + 80 – (2)(60)(80 cos 120°)
2
F = 121.7 N (ii) triangle method
sin θ = sin 120
60 121.7
θ = 25.3° above the horizontal. F

Question 2

A car travels with a velocity of 12 m s due North on a straight road. It then
–1
–1
travels due West with a velocity of 16 m s . Find the change in velocity of the car.
–1
–1
A 4 m s N 37° W C 20 m s S 37° W
–1
B 4 m s N 53° W D 20 m s S 53° W
–1
6

01 STPM Q&A PHY T1.indd 6 17/02/2022 10:03 AM