Answer:

Explanation:
- We have to make a hollow sphere of inner radius
and outer radius
.
Then the mass of the material required to make such a sphere would be calculated as:
Total volume of the spherical shell:

And the volume of the hollow space in the sphere:

Therefore the net volume of material required to make the sphere:


- Now let the density of the of the material be
.
<u>Then the mass of the material used is:</u>


Answer:
The percentage change in resistance of the wire is 69%.
Explanation:
Resistance of a wire can be determined by,
R = (ρl) ÷ A
Where R is its resistance, l is the length of the wire, A its cross sectional area and ρ its resistivity.
When the wire is stretched, its length and area changes but its volume and resistivity remains constant.
= 1.3l, and
= 
So that;
= (ρ
) ÷
= (ρ × 1.3l) ÷ (
)
= (1.3lρ) ÷ (
)
=
× [(ρl) ÷ A]
= 1.69R (∵ R = (ρl) ÷ A)
= 1.69R
Where
is the new resistance,
is the new length, and
is the new area after stretching the wire.
The change in resistance of the wire =
- R
= 1.69R - 1R
= 0.69R
The percentage change in resistance =
× 100
= 0.69 × 100
= 69%
The percentage change in resistance of the wire is 69%.
Answer:
57 N
Explanation:
Draw a free body diagram. There are three forces:
Weight force mg pulling down.
Normal force N pushing up.
Friction force F pushing horizontally.
Sum of the forces in the y direction:
∑F = ma
N − mg = 0
N = mg
Friction force is the product of normal force and coefficient of friction:
F = Nμ
F = mgμ
F = (65 kg) (9.8 m/s²) (0.09)
F = 57.3 N
Rounded, the friction force is 57 N.
Answer:
D
Explanation:
Change in speed or direction is acceleration