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An astronaut travels to another planet. Travel through this quiz for more information!

# Forces - Forces and Terminal Velocity

This GCSE Physics quiz challenges you on forces and terminal velocity. When you run as hard as you can, you soon reach a point where you can run no faster. This is your terminal velocity (or terminal speed if you are changing direction). Terminal velocity is the maximum velocity an object can reach and it depends on the magnitude of the resultant force - when it becomes zero, terminal velocity is reached. But what is it that reduces a resultant force to zero? When you are running, it is air resistance.

For the GCSE, you are expected to know that the faster an object moves through a fluid, the greater the frictional force that acts on it, as well as the speed changes of an object falling through a fluid due to the force of gravity.

1.
An astronaut travels to another planet. On this planet she records that she has a weight of 400 N. She knows from measurements back at the space centre that she has a mass of 72 kg. What is the strength of gravity on this new planet?
3.3 N/kg
5.56 N/kg
7.89 N/kg
12.23 N/kg
Rearranging the equation to g = W/m and substituting with the figures gives you the correct answer
2.
What could a horizontal line on a velocity-time graph indicate?
An object has reached terminal velocity
An object is accelerating
An object is decelerating
An object has changed direction
A velocity time graph can show you when an object is at rest, whether it is accelerating or if it is travelling at a constant speed. The gradient gives you the acceleration - a horizontal line has zero gradient which means zero acceleration. An object travelling at terminal velocity is no longer accelerating through the fluid. The area underneath a velocity-time graph will tell you the distance travelled by an object
3.
What is the weight of a person on Earth if their mass is 65 kg?
500 N
650 N
750 N
850 N
Unless you are told otherwise, assuming that the Earth's gravitational field strength is 10 N/kg is acceptable for the GCSE. In everyday language, people often refer to their weight in kilograms - in science, that is incorrect, the SI unit for weight is the newton
4.
If an object is placed into a fluid and released on Earth, what will initially happen to the object?
Accelerate
Decelerate
Move at a constant velocity
None of the above
Initially, the force of gravity is greater than the resistance force from the fluid
5.
Which statement is true for an object which is travelling through a fluid?
The slower an object moves, the greater the frictional force that acts upon it
The frictional force on an object moving through a fluid remains constant regardless of the speed at which the object moves through the fluid
The faster an object moves, the greater the frictional force that acts upon it
After an object reaches a certain speed, whilst travelling through a liquid, the frictional force acting upon it becomes zero
Fluids are liquids and gases
6.
What is the speed of an object known as when the force due to gravity and the frictional forces acting on the object are equal?
Initial velocity
Terminal velocity
Final velocity
Light speed
All objects travelling through a fluid have a terminal velocity
7.
Why does a parachute reduce a parachutist's terminal velocity?
It decreases the force of gravity exerted on the parachutist and hence reduces the parachutist's terminal velocity
It decreases the amount of air resistance exerted on the parachutist and hence reduces the parachutist's terminal velocity
It increases the amount of air resistance exerted on the parachutist and hence reduces the parachutist's terminal velocity
It increases the force of gravity exerted on the parachutist and hence reduces the parachutist's terminal velocity
This is achieved by increasing the surface area of the parachutist
8.
Which formula correctly relates the weight of an object and the force exerted on it by gravity?
W = 2 x m x g
W = m x g
W = 2g
G = W x m
This is a variation of the equation from Newton's second law
9.
What is weight measured in?
Kilograms
Newtons
Grams
Metres
Weight is measured in newtons, whilst mass is measured in kilograms
10.
The gravity on the moon is 1/6 of the force due to gravity on the Earth. What is the weight of a person on the moon who has a mass of 65 kg?
6.5 N
25 N
65 N
108 N
The mass of a person remains the same no matter where they are in the universe. The weight of an object is created by the force of gravity acting on its mass
You can find more about this topic by visiting BBC Bitesize - Forces, acceleration and Newton's Laws

Author:  Martin Moore