Everything Science Grade 11

12.3 CHAPTER 12. FORCE,MOMENTUM AND IMPULSE

direction of motion

a =?

F 1

Ff

F 1 = applied force on box (32 N)

Ff= Frictional force (7 N)

Step 2 : Calculate the acceleration of the box

We have been given:

Applied force F 1 = 32 N

Frictional force Ff= - 7 N

Mass m = 10 kg

To calculate the acceleration of the box we will be using the equation FR=

ma. Therefore:

FR = ma

F 1 + Ff = (10)(a)

32 − 7 = 10 a

25 = 10 a

a = 2,5m· s−^1 towards the left

Example 6: Newton II - box on surface 2

QUESTION

Two crates, 10 kg and 15 kg respectively, are connected with a thick rope according to the

diagram. A force of 500N is applied. The boxesmove with an acceleration of 2 m·s−^2. One

third of the total frictional force is acting on the10 kg block and two thirds on the 15 kg block.

Calculate:

1. the magnitude and direction of the frictionalforce present.


2. the magnitude of thetension in the rope at T.

15 kg

a = 2 m·s−^2

500 N

10 kg T