Answer:
D. Both occur between objects independently whether they are in contact or not.
Explanation:
- The gravitational force is a force that is exerted between two (or more) objects having mass. This force is always attractive and its magnitude is given by
where G is the gravitational constant, m1 and m2 are the two masses, and r is the distance between the two masses.
- The electrical force is a force that is exerted between two (or more) objects having electrical charge. It can be either attractive or repulsive, depending on the sign of the two charges, and its magnitude is given by
where k is the Coulomb's constant, q1 and q2 are the two charges, and r the distance between the two charges.
Looking at both formulas, we see that the two forces are present even when the two objects are not in contact with each other (in fact, r can assume any value in the formula). They are said to be non-contact forces. Therefore, the correct option is
D. Both occur between objects independently whether they are in contact or not.
Answer:
The wavelength of radio waves is 2.85 m.
(B) is correct option.
Explanation:
Given that,
Frequency = 105 MHz
We need to calculate the wavelength of radio waves
Using formula of wave velocity
Where, v = wave speed
f = frequency
= wavelength
Put the value into the formula
Hence, The wavelength of radio waves is 2.85 m.
Answer:
2/R*sqrt (g*s*sin(θ)) = w
Explanation:
Assume:
- The cylinder with mass m
- The radius of cylinder R
- Distance traveled down the slope is s
- The angular speed at bottom of slope w
- The slope of the plane θ
- Frictionless surface.
Solution:
- Using energy principle at top and bottom of the slope. The exchange of gravitational potential energy at height h, and kinetic energy at the bottom of slope.
ΔPE = ΔKE
- The change in gravitational potential energy is given as m*g*h.
- The kinetic energy of the cylinder at the bottom is given as rotational motion: 0.5*I*w^2
- Where I is the moment of inertia of the cylinder I = 0.5*m*R^2
We have:
m*g*s*sin(θ) = 0.25*m*R^2*w^2
2/R*sqrt (g*s*sin(θ)) = w
- The angular velocity depends on plane geometry θ , distance travelled down slope s, Radius of the cylinder R , and gravitational acceleration g