REVISION PHYSICS 3

```1. i. An astronaut has a mass of 5.5 x 105 g. Find his mass and his weight if he is in a flight
simulator where the gravitational attraction has been reduced to 1/6 of the earth’s pull.
ii. If an object has a mass of 50k g, find its mass and weight on the moon and
2. A boy pushes on a box of mass 45 kg and it moves at an acceleration of 7m/s2. With what force
does the boy push on the box?
3. A 250 x 1012 kg rocket is pushed with a thrust of 4000000 N. What is the acceleration of the
rocket?
If a force of 3000 N can move a crate at an acceleration of 5.8 m/s2, what is the mass of
4.
the object?
5.
Mass = 1000 kg
1000
frictional forces
i)
What is the resultant force on the car in Figure?
ii)
What is the car’s acceleration
2500N force from engine
Vectors
1. A) Complete the table to identify the physical quantities as scalars of vectors
Physical quantity
Speed
Velocity
Distance
Force
Displacement
Acceleration
Mass
Weight
Area
Volume
Scalar or vector

Hooke's Law states that the extension (spring) is proportional to the force (load) applied.
F=kxX
F is the force (load) in newtons, N
k is the 'spring constant' in newtons per metre, N/m
X is the extension in metres, m

Pressure is the amount of force applied to a known area.
𝐅𝐨𝐫𝐜𝐞 (𝐍)
𝐀𝐫𝐞𝐚(𝐦𝟐 )
Pressure =
Pressure unit in N/m2 or Pascal
1 pascal = 1 Pa = 1 N/m2.
1 kiloPa (kPa)= 103 Pa= 1000 Pa

Pressure in liquids is called hydrostatic pressure. It increases with depth and given by
this formula:
P=ρxgxh
P = Pressure (Pa)
ρ = density (kg/m3)
g = gravitational field strength
= 10 N/kg ( constant)
h = height (m)
The weight of the fluid = mass x g;
g = 10 N/kg (constant)
1. (a) A man squeezes a pin between his thumb and finger, as shown in Fig. 3.1.
finger
pin
thumb
Fig. 3.1
The finger exerts a force of 84 N on the pinhead.
The pinhead has an area of 6.0 x 10–5 m2.
(i) Calculate the pressure exerted by the finger on the pinhead.
pressure = ................................................ [2]
(ii) State the value of the force exerted by the pin on the thumb.
................................................. [1]
(iii)
Explain why the pin causes more pain on the man’s thumb than on his finger.
..................................................................................................................................
.................................................................................................................................. [1]
(a) The density of the water in a swimming pool is 1000 kg/m3. The pool is 3 m deep.
Calculate the pressure of the water at the bottom of the pool.
pressure = ……………………………… [2]
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