# Dhirendra

## Dhirendra

• Submitted By: dhirendra13
• Date Submitted: 01/15/2014 8:35 PM
• Category: Science
• Words: 863
• Page: 4
• Views: 34

SOLUTIONS TO CONCEPTS
CHAPTER – 4
1. m = 1 gm = 1/1000 kg F = 6.67 × 10–17 N  F =  6.67 × 20 r =
2 –17

Gm1m2 r2

m1 = 1 gm r

m2 = 1 gm

6.67 10 11  (1/ 1000 )  (1/ 1000 ) = r2

6.67 10 11 10 6 10 17  17 = 1 6.64 10 17 10

2.

=

1 4  o

q1 q 2 1  9  10 9 2 2 r r

The force of attraction is equal to the weight Mg =
2

For example, Assuming m= 64 kg,

4.

mass = 50 kg r = 20 cm = 0.2 m

FG  G

M

r=

3  10 4

3  10 4 = 3750 m 8 64

m1m2 6.67  10 11  2500  0.04 r2

Coulomb’s force Since, FG = Fc = q =
2

6.7 10 11  2500 6.7 10 9   25 0.04 9 10 9
= 18.07 × 10
–18 -9

q=

18.07  10 -18 = 4.3 × 10 C.
4.1

yC

r=

9 10 8 3 10 4  mt m m

q2 1 q1 q2 9 FC = = 9 × 10 0.04 4 o r 2

6.7 10 11  2500 9 10 9  q2  0.04 0.04

ol

r =

9  10 9 9  10  m  10 m

8

le

9 109 r2

ge
[Taking g=10 m/s ]
2

Ba

3.

 r = 1 = 1 metre. So, the separation between the particles is 1 m. A man is standing on the surface of earth The force acting on the man = mg ………(i) Assuming that, m = mass of the man = 50 kg 2 And g = acceleration due to gravity on the surface of earth = 10 m/s W = mg = 50× 10= 500 N = force acting on the man So, the man is also attracting the earth with a force of 500 N The force of attraction between the two charges

g.

in

Chapter-4 5. The limb exerts a normal force 48 N and frictional force of 20 N. Resultant magnitude of the force, R = = = 6.

( 48 )2  (20)2
2304  400

2704

48N

= 52 N The body builder exerts a force = 150 N. Compression x = 20 cm = 0.2 m Total force exerted by the man = f = kx  kx = 150 k=

F

x

F

7.

 2R = (R + h)  R – h – 2Rh = 0 2 2  h + 2Rh – R = 0

2

2

2

2

= –R ±

2R = R

8.

M

= 6400 × (0.414) = 2649.6 = 2650 km Two charged particle placed at a sehortion 2m. exert a force of 20m. F1 = 20 N. r1 = 20 cm F2 = ? r2 = 25 cm 1 q1q2 1 Since, F = , F 2 4 o r 2 r

yC

F1 r2  F 2 = F1 ×  F2 r12
9.

2

 r1  16 64  20    = 20 ×   = 20 × = = 12.8 N = 13 N. r  25 5  25 ...