Both spheres would hit the ground at the same time.
The spheres are dropped near to ground, so the effect of air resistance on the spheres’ resultant force is negligible.
The resultant force acting on the sphere will be its downward weight.
The ratio of the weight to mass will be 10 for each sphere, so both spheres will free-fall towards the ground at a constant acceleration of 10m/s2.
Category: Combined Physics
What are the 7 base quantities?
| Physical Quantity | SI Unit | Symbol |
| Length | metre | m |
| Mass | kilogram | kg |
| Temperature | Kelvin | K |
| Time | second | s |
| Current | ampere | A |
| Amount of substance | mole | mol |
| Luminous intensity | candela | cd |
Describe the differences between mass and weight.
| Mass | Weight |
|---|---|
| A measurement of the amount of substance in a body. | A measurement of the amount of gravitational force acting on a body |
| SI Unit: kilogram (kg) | SI Unit: newton (N) |
| Constant regardless of the gravitational field strength | Varies according to the gravitational field strength |
| Measured by a beam balance or electronic balance | Measured by a spring balance |
| Scalar quantity | Vector quantity |
What is a scalar quantity? Give some examples.
It is a physical quantity with only numerical magnitude.
Examples: mass, energy, time, volume, density, power, temperature, speed.
What is a vector quantity? Give some examples.
It is a physical quantity with both numerical magnitude and direction.
Examples: force, velocity, acceleration, weight, displacement.
What is a physical quantity?
A physical quantity is a quantity that can be measured.
It consists of a numerical magnitude and a measurement unit.
Eg, length, area, volume, velocity, acceleration
What is Brownian Motion? What causes Brownian Motion?
Brownian motion refers to the constant, random motion of small suspended particles in a fluid.
Brownian motion is caused by the constant, random bombardment of the fluid particles on the small suspended particles from all directions, causing the small suspended particles to move constantly in a haphazard motion.
Describe how a hydraulic press work.
A hydraulic press consists of two pistons of different sizes.
The space between the two pistons is filled completely with a liquid, usually hydraulic oil.
When a force is applied on the smaller piston, the pressure exerted on the liquid at the smaller piston is transmitted equally throughout the liquid.
Hence, the same pressure is also exerted at the bigger piston.
Since P = F/A, the F/A ratio will be the same at both pistons.
Since A1 < A2, hence F1 < F2.
So a smaller effort on the smaller piston (F1) will be able to lift a bigger load at the bigger piston (F2).
Double-Pivot Push-up
Describe the effects of absorbing electromagnetic waves.
Heating Effect
– Infrared heating
Fires and hot bodies emit infra-red radiation. Our skin absorbs the infra-red rays, making us feel warm.
– Microwaves heating
Microwaves are of a non-ionizing character. However, microwaves, being more penetrative, can cause more severe burns to the skin, especially when skin has high water content.
Ionisation Effect
UV rays, X-ray, Gamma ray can cause breakdown of DNA, and ionization of molecules and atoms in living matter. The mutation of these cells and atoms can lead to formation of cancerous cells.