PHYSICS KSSM FORM 4 (2.7 impulse and impulsive force)

PHYSICS KSSM FORM 4

1. PREVIOUS LESSON
•Linear motion equation
•Inertia
–effect of inertia
•Momentum
–Types of collisions
•Force
–Newton’s Second Law

2. 2.6 ANALYSING
IMPULSE AND
IMPULSIVE FORCE

3. Students must be able to:
1. to state impulse and impulsive force.
2. to analyse the problem involving impulse and
impulsive force.

6. u = 0 m/s v = 10 m/s
u = 0 m/s v = 40 m/s
Time taken

7. IMPULSE
The product of force, F and the time
interval, t during the force acts.
Impulse, J = Force x time
= Ft
F = apply force
t = time of action of force
UNIT : Newton.Second (N s) @ kg m/s

8. IMPULSE also known as change of
momentum
We know that F = ma
a = (v –u) / t
F = (mv –mu ) /t
Rearrange the equation
Ft = mv -mu

9. IMPULSIVE FORCE
As the rate of change of momentum
during collision or explosion.
Unit Force is Newton, N.

13. Effects of impulse vs Force
A force determines the acceleration
(rate of velocity change) of an
object. A greater force produces a
higher acceleration.
An impulse determines the velocity
change of an object. A greater
impulse yield a higher velocity
change.

14. •Impulsive force inversely proportional with
time
•Therefore to reduce impulsive force, we
need to increase time impact.

15. Self Assess
1.A force F acts on a 6 kg object at rest
on a smooth surface. If the velocity of
the object increase to 2 m/s in 6 s,
what is the value of F? (2 N)
2.An object of mass 2 kg is acted on by
a force which cause the velocity of
the object to increase from 1 m/s to 9
m/s. what is the impulse on the
object? (16 Ns)

16. 3. Danish kicks a ball with force of 1500N. The
time contact of his boot with the ball is 0.008s.
What is impulse delivered to the ball? If the
mass of the ball is 0.5 kg, what is velocity of
the ball? ( 24 m/s)
4. A 0.045 kg golf ball strikes a wall at a speed
of 30 m/s and rebounds at speed of 20 m/s.
what is the impulse on the ball? If the force on
the ball is 500 N, find the contact time of the
ball with the wall?(0.0045 s)

17. •5. A baseball of mass 0.14kg moving at
40 m/s is struck by a bat and rebound
at 60 m/s. given that the time contact is
0.05s,find force exerted on the ball? (
280N)
•6. In a crash test, a car of mass 1500 kg
crashes into a wall at 15 m/s. it
rebounds at 2 m/s. if the collision time
is 0.18s find the force excertedon the
car ? (1.42e5 N)