**Answer **

(C).

When there is an angle between the two directions, the cosine of the angle must be considered.

**Step by step Solution**

The work done by a force is defined as the product of the force and the distance traveled in the direction of motion.

The first answer "Only the component of the force perpendicular to the motion is used to calculate the work" is wrong because, the force perpendicular to motion does no work.

The second choice "If the force acts in the same direction as the motion, then no work is done" is wrong because the work in the direction of the force is .

Fourth answer "A force at a right angle to the motion requires the use of the sine of the angle" is wrong because the meaning that there is no work done in the direction perpendicular to the motion.

The third answer" When there is an angle between the two directions, the cosine of the angle must be considered." is correct because the work is calculated using the force in the direction of the motion. The magnitude of this force is

**Answer:**

**Explanation:**

The time period of the simple pendulum is given by :

l is the length of the pendulum

g is the acceleration due to gravity

We have,

T = 1.4 s, l = 1 m

So,

**So, the acceleration due to gravity of that planet is **.

Answer:

True

Explanation:

External forces such as extreme weather pose a constant threat to the structural reliability of structures.

Extreme weather conditions such as a high temperature or rainfall have an effect on structures due to the constant exposure of the structures to this factors. The materials used in building these structures have different properties which are usually affected by environmental factors.

**Answer:**D) in a straight line.

Hey

Newton's first law says that if an object is at rest it will stay at rest. But if it is moving it will continue moving in a straight line if there is no external force. If there where no gravity the object that you throw will keep going in a straight line according to Newton's first law.

**Answer:**

two-slit interference model was proposed by Young d sin θ = m λ

**Explanation:**

The two-slit interference model was proposed by Young, it establishes that if a coherent source of light passes through two slits, the shape of the given pattern is a consequence of the relative phase difference between the two rays; mathematically it can be expressed by

d sin θ = m λ

m= 0, 1, 2, 3, ...

for constructive interference, that is, the two rays arrive with a number between wavelengths.

D is the distance between the slits, tea the angle between the two rays, m an integer and m the wavelength used.

In a simulation a pattern of slits of equal intensity and equally spaced is observed.