Everything Science Grade 11

12.4 CHAPTER 12. FORCE,MOMENTUM AND IMPULSE

Step 3 : Situation on Earth

wE = mgE= G

mE· m

r^2 E

= (70kg)(9,8m· s−^2 )

= 686N

Step 4 : Situation on Beeble interms of situation on Earth

Write the equation for the gravitational force onBeeble and then substitute the

values for mBand rB, in terms of the values for the Earth.

wB= mgB = G

mB· m

r^2 B

= G

1

2 mE· m

(^14 rE)^2

= 8(G

mE· m

r^2 E

)

= 8wE

= 8(686N)

= 5488N

Step 5 : Quote the final answer

The man weighs 5 488N on Beeble.

Exercise 12 - 6

1. Two objects of mass2m and 3m respectively exert a force F on each other when they area
   certain distance apart.What will be the forcebetween two objects situated the same distance
   apart but having a massof 5m and 6m respectively?

(a) 0,2 F

(b) 1,2 F

(c) 2,2 F

(d) 5 F

2. As the distance of anobject above the surfaceof the Earth is greatly increased, the weight of the
   object would

(a) increase

(b) decrease

(c) increase and then suddenly decrease

(d) remain the same

3. A satellite circles around the Earth at a height where the gravitationalforce is a factor 4 less than
   at the surface of the Earth. If the Earth’s radiusis R, then the height ofthe satellite above the
   surface is:

(a) R

(b) 2 R

(c) 4 R