The kinds of Force

1. Weight(w)w = m. gw = weight ( N )m = mass ( kg )g = gravitational acceleration ( m/s2 )

w

2. Normal Force (N)

• Normal force is the contact force which acts in perpendicular direction to the contact plane.

• w = N w ≠ N• N = w cos α

N

ww

N

α

3. String Tension Force ( T )

• String tension Force is the force which is transmitted through a string or wire

T

TTT

F

4. Friction Force ( f )

• Force which opposes the direction of objects motion is frictional force.

f

vF

Friction force

Free body diagram

• N = w

w

N

T = ww

T

N = w cosα

N

WW sin α

W cos α

exercise

• 1. a cube at rest on smooth floor receives a horizontal force of 100 N and moves accelerated. If the cube has 5 kg in mass determine :

• A. acceleration of cube• B. distance travelled by the cube after 10

second

2. An object is rest on a smooth floor and it is applied force as in the following figure,if the object moves 10 m at 5 s, determine :a. acceleration of the objectb. mass of objectc. Normal force.

120 N

80 N

45o

3. Two object each 2 kg and 1 kg is connected with a string and pulled by a constant force of 24 N, as shown in the figure, then the magnitude of the string tension force is …

2 kg 1 kg

4. Look at the following figure, based on the figure determine the string tension force of T1 and T2 :

12 kg

8 kg

T1

T2

5. look at following figure,based of figure determine :a. Free body diagramb. the system accelerationc. force resultan on each cubed. contact force on each cube

15kg 20 kg

45 kg

F=400N

6. Look at the values of the following figure. If the mass of the object is 20 kg, the values of the tension strength between T1 and T2 are …

T1 T2

60o

30o

T

7. A person with mass 60 kg is in lift which a moving downward with acceleration 3 m/s2. The presure of the person on the lift floor if the gravitational acceleration is 10 m/s2 is …

8. Look at the pulley system in the following figure. The masses of the load A and B are 5 kg and 3 kg respectively. Calculate acceleration of the blocks system and tension of the string.

A

B