Forces and pressure

Question 1

What is the SI unit of force?

Answer 1

The SI unit of force is the newton (N).

Question 2

Is air resistance a contact force?

Answer 2

Yes

Question 3

Is normal a contact force?

Answer 3

Yes

Question 4

Is tension a contact force?

Answer 4

Yes

Question 5

What are the three non-contact forces?

Answer 5

Gravitational force, electrostatic force and magnetic force.

Question 6

What is inertia?

Answer 6

Mass of a body resists a change in the state of rest or motion of the body(Inertia)

Inertia is the resistance of an object to a change in its motion when a force is applied.

Question 7

What is the formula to finding force?

Answer 7

W=mg
Weight (N)
Mass (kg)
g (9.81n/kg)

Question 8

What is use to measure the amount of force applied?

Answer 8

A spring balance.

Question 9

When more people board a ship, what happens to the upthrust and weight?

If Upthrust increase/decrease/ remain the same
Then weight increase/ decrease/remain the same

Answer 9

Increase in upthrust causes an increase in weight which makes it balanced.

Question 10

What is the formula of pressure?

Answer 10

Pressure= Force/Area
(Pa)=1N/m squared

Question 11

What are the two factors affecting pressure?

Answer 11

Force and area.

Question 12

Explain how the suction cup can hold a light load without falling off the wall.

Answer 12

When pressed against the wall, the air is forced out of the suction cup, forming a low pressure region. (1) The higher atmospheric pressure presses/forces/ pushes the cup hook against the wall or exert on a normal force on the hook by the wall (1) This increases the upward frictional force that balances the downward gravitational force on the suction and objects hung on its hook.

1. Air pushed out
2. Higher atmospheric pressure outside suction cup while lower pressure region in the suction cup.
3. Normal force
4. Increase frictional force
5. Balance gravitational force.

Question 13

A parachutist jumps out of a plane. He falls towards the ground at increasing speed. Upon opening his parachute, he starts falling towards the ground at constant speed.
Which statement is correct?

A The parachutist’s speed increases as the downward force on the parachutist and his closed parachute increases.
B There are no forces acting on the parachutist after he opened his parachute.
C The upward force on the parachutist due to his open parachute is equal to their combined weight.
D The upward force on the parachutist due to his parachute remains constant throughout the entire process.

Answer 13

C

Question 14

Two solid rectangular blocks made of the same material are placed on the ground. The larger block has thrice the length and breadth, but has the same height as the smaller block.

Smaller block:
2x length
X breadth
X height
Larger block:
6x length
3x breadth
X height

Which statement is correct?
A Both blocks exert the same pressure on the ground.
B The larger block exerts thrice the pressure of the smaller block on the ground.
C The smaller block exerts half the pressure of the larger block on the ground.
D The smaller block exerts thrice the pressure of the larger block on the ground.

Answer 14

A

Question 15

How do you measure mass?

Answer 15

use an electronic scale

Question 16

What do you need to take note when you are using an electronic scale to measure mass?

Answer 16

Check that if the initial reading before putting any object on the electronic scale is zero, if it is not zero, need to press the tare button.

Question 17

What does a spring balance measure? What do you need to take note of when using a spring balance?

Answer 17

A spring balance measure the weight AKA force of an object.

Step 1: Ensure the “0” mark of the scale is in line with the pointer.
If it isn’t, move the scale by pulling or pushing the tab until the “0” mark is in line with the pointer.
Step 2: Apply the force to be measured on the hook
Step 3: read the scale to the nearest 1 d.p.
Also avoid parallax error

Question 18

What is the relationship between kg and N?

Answer 18

1kg=10N ——> WRONG
____kg x 9.81N/kg = ___N

Question 19

Compare the effects of balanced and unbalanced forces on an object’s motion.

Answer 19

Balanced forces means that the resultant force acting on an object is zero.

When forces on an object at rest are balanced, the object will remain at rest.
When forces on a moving object are balanced, the object will continue moving with constant speed and direction (i.e. constant. Velocity)

Unbalanced forces means that the resultant force acting on an object is not zero. This could happen when the pushing force is larger than the friction or when the pushing force is removed, and only friction is acting in the horizontal direction.

If resultant force is in the same direction as the motion of the object, the object’s speed increases (i.e. accelerates)

If the resultant force opposes the motion of the object, the object’s speed decreases (i.e. decelerates).

Question 20

Analyse the role of friction in various real-life situations, such as braking in cars.

Answer 20

Friction opposes motion, converting kinetic energy to heat, which is essential for braking in cars. However, excessive friction can cause wear and energy loss. (Remember that this answer is generated by ChatGPT so need to check with teacher)

Question 21

Compare the effects of gravitational force on objects with different masses.

Answer 21

Gravitational force is proportional to mass (W=mg), meaning heavier objects experience greater force. However, in free fall, all objects accelerate at the same rate regardless of mass.
(Remember that this answer is generated by ChatGPT so need to check with teacher)

Question 22

Compare the difference in the change of pressure in sea vs in the air.

Answer 22

The deeper you go under the sea, the greater the pressure of the water pushing down you.
(for every 10 metres you go down, the pressure increases by one atmosphere)

the higher you ascend into the air when taking an airplane, the higher the pressure you feel.