Q: A goods lorry of mass 4000 kg is loaded with goods of mass 20000 kg and moves with a velocity of 2 m/s. What is its momentum?

$p = (4000 + 20000) \times 2 = 48000\ \text{kg m/s}$

Q: If a force of 2 N acts on a body and changes its velocity uniformly from 2 m/s to 5 m/s in 10 s, what is the mass of the body?

$m = \frac{F \times t}{v - u} = \frac{2 \times 10}{5 - 2} = \frac{20}{3} \approx 6.67\ \text{kg}$

Q: A 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a horizontal track. If the engine exerts a force of 40000 N and the track offers a friction force of 5000 N, what is the net accelerating force?

$F_{net} = 40000 - 5000 = 35000\ \text{N}$

Question 1

Which of the following statements best describes inertia?

Accepted Answer

Inertia is the property of matter by which it tries to maintain its state of rest or uniform motion along a straight line.

Question 2

A football and a rock of the same size are placed side by side. Which one has more inertia and why?

Accepted Answer

The rock, because it has greater mass.

Question 3

Which of the following is NOT an effect of force on an object?

Accepted Answer

Force can change the color of an object.

Question 4

A person standing in a moving bus falls forward when the driver suddenly applies the brakes. This is best explained by:

Accepted Answer

Inertia, as described by Newton's first law of motion.

Question 5

Which of the following equations correctly represents Newton's second law of motion?

Accepted Answer

$F = m 	imes a$

Question 6

A goods lorry of mass 4000 kg is loaded with goods of mass 20000 kg and moves with a velocity of 2 m/s. What is its momentum?

Accepted Answer

$p = (4000 + 20000) 	imes 2 = 48000\ 	ext{kg m/s}$

Question 7

Which of the following scenarios is an example of Newton's third law of motion?

Accepted Answer

A swimmer pushes water backward to move forward.

Question 8

If a force of 2 N acts on a body and changes its velocity uniformly from 2 m/s to 5 m/s in 10 s, what is the mass of the body?

Accepted Answer

$m = \frac{F 	imes t}{v - u} = \frac{2 	imes 10}{5 - 2} = \frac{20}{3} \approx 6.67\ 	ext{kg}$

Question 9

Which of the following best describes a balanced force?

Accepted Answer

Forces that are equal in magnitude and opposite in direction, resulting in no change in motion.

Question 10

A 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a horizontal track. If the engine exerts a force of 40000 N and the track offers a friction force of 5000 N, what is the net accelerating force?

Accepted Answer

$F_{net} = 40000 - 5000 = 35000\ 	ext{N}$

Question 11

Which of the following is the correct SI unit of force?

Accepted Answer

Newton

Question 12

A fielder pulls his hands backwards while catching a fast-moving cricket ball. What is the main reason for this action?

Accepted Answer

To increase the time over which the ball's momentum decreases, reducing the force of impact.

Question 13

Which of the following is the mathematical expression for momentum?

Accepted Answer

$p = m 	imes v$

Question 14

Why does a gun recoil backward when a bullet is fired?

Accepted Answer

Because the gun exerts a forward force on the bullet and the bullet exerts an equal and opposite force on the gun.

Question 15

Which of the following is NOT a real-life example of inertia?

Accepted Answer

A swimmer pushes water backward to move forward.

Question 16

If the mass of a body is doubled and its acceleration is halved, what happens to the force acting on it?

Accepted Answer

The force remains the same as before.

Question 17

Which of the following best explains why seat belts are used in cars?

Accepted Answer

To prevent passengers from moving forward due to inertia in case of sudden braking or accident.

Question 18

Which law of motion explains why a swimmer pushes water backward to move forward?

Accepted Answer

Newton's third law of motion.

Question 19

A karate player uses a quick, powerful strike to break a slab of ice. Which concept does this best illustrate?

Accepted Answer

Applying a large force over a very short period to generate high acceleration.

Force and Laws of Motion: Study Notes

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