Speed

1) When we move an object such as a ball, it will move.

2) A moving ball is either fast or slow depending its speed.

3) Speed is the rate of movement of an object.

4) The object which moves faster travels a longer distance in a given time.

Rocket has the fastest speed. (Faster time reach destination)

Car has slower speed than rocket (Slower time reach destination)

CALCULATION OF SPEED

1) Speed of a moving object can be calculate if we know the distance it has travelled and the time taken to travel the distance.

2) The units for speed are:
    a. cm per second (cm/s),
    b. metre per second (m/s),
    c. kilometre per hour (km/h).

3) The speed of an object can be calculated by using the following formula:



                             Speed  =     Distance   
                                                      Time
Example :
    a. A lorry takes three hours to reach a destination of 240 km away.

 

                             Speed =            240  

                                                        3

                                       = 80 km/j

    b. A toy car takes 2 minutes to travel a distance of 50 cm.

                             Speed =             50   

                                                        2

                                      = 25 cm/min

Force and Energy (Worksheets)

Section A
1) Write TRUE or FALSE for each statement below.

  a) Friction is a force that goes against the direction of an object's movement.                                

  b) The treads of a tyre reduce the friction produced when a car moves.                                          

  c) It is easier to push a box over grass than over a marble floor.                                                      

  d) A hovercraft reduces friction by forming an air cushion below it when it moves.                            

2) Underline the correct words for the statements below.

  a) Pushing and pulling are (forces, energy)

  b) When an object moves towards you, you are (pulling , pushing it)

  c) When you are pushed, you can (see, feel) the force on you.

  d) A combination of pushing and pulling is called (friction, twisting).

  e) (Cycling, Dragging ) uses a pushing force.

Section B
1) The following information shows four situations

   P - A flag waves in the wind
   Q - A plasticine changes shape when it is squeezed
   R - A moving ball moves faster when it is kicked
   S- A moving marble on a surface will eventually stop

Which shows the effects of force
  A. P and Q
  B. P, R and S
  C. Q, R and S
  D. P, Q, R and S

2)Wong Nam wants to find out how the mass of an object can affect friction. What should he keep the same in his investigation to make the test fair?

I- The surface on which the object moves
II- The distance the object travels
III- The force applied to make the object move

A. I and II only
B. I and III only
C. II and III only
D. I, II and III

3) Which of the following are not factors that affect friction?

I- Surface are of objects in contact
II- Mass of an object
III- Roughness of a surface
IV- Speed of a moving object

A. I and II only
B. I and IV only
C. II,III and IV only
D. I, II, III and IV

4) What are the advantages of friction?

I- Objects can be held without slipping
II- Wears out the brake pads of a bicycle
III- People can walk without slipping and falling
IV- Rusty hinges make doors hard to push

A. I and III only
B. I, II and IV only
C. II and III and IV only
D. I, II and III and IV

5) What is meant by friction?

A. It is a force that pulls objects to the ground
B. It is a force that makes objects move
C. It is a force that goes against a moving object
D. It is a force that can be seen.

6) A plastic bottle becomes crushed when squeezed. What is proven in this activity?

A. Force changes the position of an object
B. Force moves a stationery object
C. Force changes the direction of a moving object
D. Force changes the shape of an object.

7) The information below shows three situations

P- The ball stops moving when blocked
Q- The movement of a marble changes when an opposing force is applied on it
R- A can becomes crushed when squeezed

What situations show the effects of force?

A. P and Q
B. P and R
C. Q and R
D. P, Q and R




Section A
1) (a) TRUE  (b)FALSE  (c)FALSE ( d)TRUE
2) (a)Force (b)pulling (c)feel (d) twisting (e) Cycling

Section B
1)D 2)B 3)B 4)A 5)B 5)

Friction

Let's watch the video below to at least understand the concept of friction before lesson starts. Enjoy ;)

Friction is a force that opposes the movement of an object which it can occur when two surfaces are in contact with each other. Hence, friction is known as a type of force.Friction slows down the movement of an object.

A marble moves faster on glass surface (Smooth surface)

A marble moves slower on rough surface (sand paper)

There are some effects of friction such as :

1) makes the surfaces warm, 

2) makes it hard to move a heavy object,

3) causes wear and tear of surfaces of objects,

4) makes a moving object slow down and stop, 

5) enable an object to stay in a stationary position. 

The causes of friction are depending on : 

1) condition of surface- a smooth surface produces a smaller friction, while a rough surface produces a    greater friction,

2) the weight of object- a heavier object produces a greater frictional force.

Benefits of friction :

1) allows us to walk or run without slippping

2) allows a moving vehicles to slow down or stop

3)enables us to hold things, 

4) enables us to sharpen a knife.

Drawbacks of friction :

Friction cause tyres to wear out

1) causes the soles of tyres and shoes to wear out

2) produces heat in machines

3) causes wasting  of energy

Methods to reduce friction :

1) using rollers or ball bearings,

Ball bearing and oil can reduce friction

2) using lubricants such as oil, wax or grease,

3) smoothening the surfaces.

4) using an aerodynamic shape.

Effects Of A Force

1) A force can cause a change in the motion and shape of an object.

2) A force makes a stationary object move.

3) A force can faster, slow down or stop a moving object

4) A force changes the motion of an object as shown and the shape of an object