2.1 A crate of mass 2 kg is being pulled to the right across a rough horizontal surface by a constant force F. The force F is applied at an angle of 20° to the horizontal, as shown in the diagram below. The diagram shows a crate with a mass of 2 kg and a force F applied at 20° to the surface. A constant frictional force of 3 N acts between the surface and the crate. The coefficient of kinetic friction between the crate and the surface is 0.2. Calculate the magnitude of: 2.1.2 Normal force acting on the crate. 2.1.3 Force F. 2.1.4 Acceleration of the crate. 2.2 A massive rock from outer space is moving towards the Earth. 2.2.1 State Newton's Law of Universal Gravitation in words. 2.2.2 How does the magnitude of the gravitational force exerted by the Earth on the rock change as the distance between the rock and the Earth becomes smaller? Choose from INCREASES, DECREASES or REMAINS THE SAME. Give a reason for the answer.

NSC Physical Sciences Mechanics: Force and Newton’s Laws: 2.1 A crate of mass 2 kg is bein

2.1 A crate of mass 2 kg is being pulled to the right across a rough horizontal surface by a constant force F - NSC Physical Sciences - Question 2 - 2017 - Paper 1

Question 2

2.1 A crate of mass 2 kg is being pulled to the right across a rough horizontal surface by a constant force F. The force F is applied at an angle of 20° to the hori... show full transcript

Worked Solution & Example Answer:2.1 A crate of mass 2 kg is being pulled to the right across a rough horizontal surface by a constant force F - NSC Physical Sciences - Question 2 - 2017 - Paper 1

Step 1

Draw a labelled free-body diagram showing ALL the forces acting on the crate.

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Answer

To draw the free-body diagram, label the forces as follows:

Weight (W) of the crate downward, equal to the mass times the gravitational acceleration:
$W = mg = 2 ext{ kg} imes 9.8 ext{ m/s}^2 = 19.6 ext{ N}$
Normal Force (N) acting upward, vertically opposite to weight.
Friction Force (f) acting opposite to the direction of applied force F, given as 3 N.
Applied Force (F) has two components:
1. Horizontal component ( $F_x = F imes ext{cos}(20°)$ )
2. Vertical component ( $F_y = F imes ext{sin}(20°)$ )

The diagram should show these forces with arrows indicating their direction.

Step 2

Normal force acting on the crate.

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Answer

Using the equilibrium of forces in the vertical direction, we have: $N + F_y - W = 0$ Substituting for $F_y = F imes ext{sin}(20°)$ and $W = 19.6 ext{ N}$ :

Calculate $F_y$ after finding F.
Therefore: $N = W - F_y$
After substitution, you would assess based on the calculated $F$ .

Step 3

Force F.

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Answer

The applied force F can be calculated using the horizontal component and given friction force:
From the equation of motion: $F_x - f = ma$ Substituting $F_x = F imes ext{cos}(20°)$ , we get
$F imes ext{cos}(20°) - 3 = 2 imes a$ Using $a$ from 2.1.4 after completion.

Step 4

Acceleration of the crate.

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Answer

From the formula of force and using $F$ found in the previous step, we can find the acceleration: $F_x = ma$ Substituting the values and solving gives: $a = rac{F_x - f}{m}$ Thus using $F_x$ calculated, plug in values to find the acceleration.

Step 5

State Newton's Law of Universal Gravitation in words.

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Answer

Any two particles (objects) in the universe will attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

Step 6

How does the magnitude of the gravitational force change?

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Answer

The gravitational force increases as the distance between the rock and the Earth decreases. This is based on the inverse square relationship in the law of gravitation, which states that as distance decreases, the force increases.

2.1 A crate of mass 2 kg is being pulled to the right across a rough horizontal surface by a constant force F - NSC Physical Sciences - Question 2 - 2017 - Paper 1

Worked Solution & Example Answer:2.1 A crate of mass 2 kg is being pulled to the right across a rough horizontal surface by a constant force F - NSC Physical Sciences - Question 2 - 2017 - Paper 1

Draw a labelled free-body diagram showing ALL the forces acting on the crate.

Normal force acting on the crate.

Force F.

Acceleration of the crate.

State Newton's Law of Universal Gravitation in words.

How does the magnitude of the gravitational force change?

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