Impulsive force (slideshow)

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01

Are you ready to learn?

02

IMPULSE AND IMPULSIVE FORCE

03LEARNING OUTCOMES

• Define impulse and impulsive force

• Explain the effects of increasing or decreasing time of impact on impulsive force

• Describe situations where an impulsive force is beneficial

• Solve problems involving impulsive force

04

05

DEMONSTRATION

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06DESIGN AN EXPERIMENTWhat can we do to investigate the impulsive force?

Materials:

Eggs

Newspapers

Sponges

07Relationship between contact

time and force

• Manipulated variables: ??

• Responding variables: ??

• Controlled variables:??

08RESULT & OBSERVATION

Surface types

Contact time

Observation on egg

Force

Table Longer / Shorter

Break / Did not break

Larger / Smaller

Sponge Longer / Shorter

Break / Did not break

Larger / Smaller

tF

1

09Relationship between force and

change in momentum

Before

After

Is the egg experience any changes in momentum?

mupinitial

mvp final

10• So, the change in momentum is:

• What happens to the force when the change of momentum is higher?

initialfinal ppp

mumvp

pF

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11CONCLUSION

-The contact time on impact is affected by the hardness of surface. The harder the surface, the shorter the contact time on impact

-When contact time is shortest, the force of impact will be larger

-The force is directly proportional to the change in momentum

12

• Relationship with impulsive force

• Impulsive force:

• So, the impulsive force is the rate of change of momentum

pF t

F1

t

mumvF

NkgmsF /2

Example:

A bullet of mass 50 g is shot and it travels at a velocity of 100 m/s towards a target and takes 0.01 seconds to come to a stop. What is the impulsive force hitting the target?

• HOW ABOUT IMPULSE?

• Impulse is defined as the changes of momentum

mumvFt

Nskgms /1

Example:

• Figure shows a ball of mass 20 g travelling at 15m/s. It hits a wall and bounces back in opposite direction with a velocity of 12m/s. What is the impulse of the ball?

13APPLICATION OF IMPULSIVE FORCE

Both cars travel at a velocity of 120 m/s and hits a wall. Why does the impact on car A is smaller compared to car B?

A B

• Diagram 2 shows a baseball player wearing a soft thick glove to catch a ball during a baseball match. Compare the impulsive force if the baseball player wears a hard glove to catch the ball. 

14

• Why a karate expert can break a pile of plank easily using his bare hand?

• Why does food stuff such as garlic can be pounded using mortar and pestle?

15

What are other applications of impulsive force in our daily lives?

Can you explain??

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16Do you want to play some

games?INSTRUCTIONS:

-You are allowed to discuss during the game

-The task for each player is to calculate the questions given

-Given that initial velocity of the ball is 0 ms-1 and mass of the ball is 2 kg. The result of the calculation will determine whether it’s a goal or a miss

17Kick no. Final

velocity (v)

Time of impact

(t/s)

Impulsive force (F/N)

Result of the kick

1 45 0.3 300 GOAL / MISSED

2 25 0.2 250 GOAL / MISSED

3 30 0.6 100 GOAL / MISSED

4 30 0.2 300 GOAL / MISSED

5 30 0.6 100 GOAL / MISSED

6 10 0.8 25 GOAL / MISSED

Initial velocity (u) = 0 m/s

Mass of ball (m) = 2kg

18 What have you learn today?• Impulse as rate of change of momentum

• Impulsive force as the rate of change of momentum in a collision between 2 objects

• Explain the effect of increasing & decreasing time of impact on the magnitude of the impulsive force

• Describe situations and solve problems involving impulsive force

mumvFt

t

mumvF