Q: A 5 kg object is dropped from rest. Ignoring air resistance, what is the force of gravity acting on it?

$$F_g = mg = 5 \times 9.8 = 49\ \mathrm{N}$$

Question 1

According to Newton's Second Law, what happens to the acceleration of an object if the net force acting on it is doubled while its mass remains constant?

Accepted Answer

The acceleration is doubled.

Question 2

Which of the following best describes the relationship between mass and weight?

Accepted Answer

Weight is the force due to gravity acting on mass, and is given by $$w = mg.$$

Question 3

A 10 kg box is pushed with a net force of 30 N. What is its acceleration?

Accepted Answer

$$a = \frac{F_{net}}{m} = \frac{30}{10} = 3\ \mathrm{m/s^2$}$$

Question 4

Which statement about static and kinetic friction is correct?

Accepted Answer

Static friction prevents motion up to a maximum value, while kinetic friction acts during motion.

Question 5

A skydiver jumps from a plane and eventually reaches terminal velocity. Which of the following is true at terminal velocity?

Accepted Answer

The force of gravity equals the force of air resistance.

Question 6

If the mass of an object is doubled while the net force remains the same, what happens to its acceleration?

Accepted Answer

The acceleration is halved.

Question 7

Which of the following best explains why astronauts feel 'weightless' while orbiting Earth?

Accepted Answer

They are in free fall, accelerating at the same rate as their spacecraft.

Question 8

A 5 kg object is dropped from rest. Ignoring air resistance, what is the force of gravity acting on it?

Accepted Answer

$$F_g = mg = 5 	imes 9.8 = 49\ \mathrm{N}$$

Question 9

Which of the following statements about air resistance is correct?

Accepted Answer

Air resistance acts opposite to the direction of motion and increases with speed.

Question 10

A car of mass 1000 kg accelerates from rest under a net force of 4000 N. What is its acceleration?

Accepted Answer

$$a = \frac{4000}{1000} = 4\ \mathrm{m/s^2$}$$

Question 11

Which of the following is NOT a correct statement about mass?

Accepted Answer

Mass changes depending on the gravitational field.

Question 12

A 70 kg parachutist jumps from a plane. If the force of air resistance is 350 N upward and the force of gravity is 686 N downward, what is the net force acting on the parachutist?

Accepted Answer

$$F_{net} = 686 - 350 = 336\ \mathrm{N}$$ downward

Question 13

Which of the following best describes terminal velocity?

Accepted Answer

The speed at which the net force on a falling object is zero.

Question 14

A block is sliding across a table and slows down due to friction. Which force is primarily responsible for this deceleration?

Accepted Answer

The kinetic friction force.

Question 15

If a 2 kg object experiences a net force of 10 N, what is its acceleration?

Accepted Answer

$$a = \frac{10}{2} = 5\ \mathrm{m/s^2$}$$

Question 16

Which of the following is true about the direction of frictional force?

Accepted Answer

It acts opposite to the direction of motion or attempted motion.

Question 17

A 50 kg crate is pulled with a force of 200 N. If the frictional force is 50 N, what is the acceleration of the crate?

Accepted Answer

$$a = \frac{200 - 50}{50} = 3\ \mathrm{m/s^2$}$$

Question 18

Which of the following scenarios best illustrates Newton's Second Law?

Accepted Answer

A car accelerating when the driver steps on the gas pedal.

Question 19

If two objects of different masses are dropped from the same height in the absence of air resistance, which will hit the ground first?

Accepted Answer

Both will hit the ground at the same time.

Question 20

Which equation correctly expresses Newton's Second Law?

Accepted Answer

$$F_{net} = m a$$

Question 21

A 60 kg person stands on Earth and on the Moon (where $$g_{moon} = 1.6\ \mathrm{m/s^2$}). $$What is the person's weight on the Moon?

Accepted Answer

$$w = 60 	imes 1.6 = 96\ \mathrm{N}$$

Newton’s Second Law: Forces, Friction, Mass, Weight, and Acceleration

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