Page 20 - Pra U STPM 2021 Penggal 1 - Physics

Physics Term 1 STPM Chapter 2 Kinematics

Vertical component of velocity when bullet hits the ground v y = u + at
= 0 + 9.81 × 0.639
v x = 6.27 m s –1

2 2
Speed of bullet v = v x + v y
θ = 20 + 6.27
2
2
v y v
= 21.0 m s –1 2
v y
tan θ =
v x
6.27
=
20
θ = 17.4°

Quick Check 4

1. A stone is thrown from O and follows a v/m s –1 h/m
parabolic path. The highest point reached is P. A 20 15
Which of the following is zero at the highest B 20 25
point P? C 15 25
A Acceleration D 25 20
B Vertical component of velocity 4. An aeroplane flying in a straight line at
C Kinetic energy constant height of 2 000 m with a speed of
D Momentum 200 m s drops an object. The object takes
–1
2. A projectile is fired with an initial velocity a time t to reach the ground and travels a
–2
u at an angle θ to the horizontal. Neglecting horizontal distance s. Taking g as 10 m s and
air resistance, the horizontal distance x it has ignoring air resistance, which of the
travelled, and the height y reached after a following gives the values of t and s?
time t are t s
1 A 200 s 10 km
A x = ut sin θ, y = ut cos θ – gt 2
2 B 100 s 05 km
1
B x = ut sin θ – gt , y = ut cos θ C 020 s 04 km
2
2 D 010 s 02 km
1
C x = ut cos θ, y = ut sin θ + gt 2
2
1 5. A bullet is fired horizontally from the top
D x = ut cos θ, y = ut sin θ – gt 2
2 of a cliff on the surface of the earth with a
–1
speed of 40 m s . Assuming no air resistance,
3. A projectile is fired with a horizontal velocity what is the speed of the bullet 3 s later?
v from a height h as shown in the figure. (g = 10 m s )
–2
It strikes the ground at an angle of θ to the A 30 m s C 50 m s –1
–1
horizontal. Which of the following values of v B 40 m s D 70 m s –1
–1
and h will give the greatest value of the angle θ?
v 6. A projectile leaves the ground at an angle of
60° to the horizontal. Its initial kinetic energy
is K. Neglecting air resistance, find in terms of
h K its kinetic energy at the highest point of the
motion.
θ
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02 STPM PHY T1.indd 49 4/9/18 8:19 AM