Physics - Forces
AQA GSCE Old specification physics P2
- Created by: EMayH
- Created on: 03-04-10 12:07
Question 1.
What can you say about the forces acting on a stationary object or an object travelling at a constant speed?
Answer 1.
They are equal and opposite
Question 2.
What is the unit of force?
Answer 2.
The Newton (N)
Question 3.
What is the 'resultant force'?
Answer 3.
A number of forces acting on an object that are replaced by a single force that has the same effect as the original forces acting together.
Question 4.
What happens if the resultant force is zero?
Answer 4.
The object remains stationary if it was at rest
Or
Continues to move at the same speed in the same direction if it was already moving.
Question 5.
What is the equation for resultant force?
Answer 5.
Resultant force = mass x acceleration
(newtons,N) (kg) (m/s squared)
Question 6.
What happens if the resultant force is in the same direction as the velocity?
Answer 6.
The velocity of the object increases. This is positive acceleration.
Question 7.
What happens if the resultant force is opposite to the direction of the velocity?
Answer 7.
The velocity of the object decreases and we call this negative acceleration (or decceleration)
Question 8.
Name three factors that increase thinking distance.
Answer 8.
- Tiredness,
- Alcohol
- Drugs
All of these increase reaction times
Question 9.
Name three factors that increase braking distance.
Answer 9.
- The speed the vehicle is travelling - faster = bigger braking distance
- The road/ weather conditions - icy or wet roads mean the driver has to break with less force to avoid skidding therefore increasing braking distance
- Contition of the vehicle - eg. worn tyre treads reduce friction - increase braking distance.
Question 10.
What is the equation for stopping distance?
Answer 10.
Stopping distance = thinking distance + braking distance
Question 11.
What is the difference between mass and weight?
Answer 11.
Weight = The force of gravity on an object and is measured in Newtons (N)
Mass = The quantity of matter in an object and is measured in grams/kilograms (g/kg)
Question 12.
What is gravitational field strength and what is it measured in?
Answer 12.
Gravitational field strength is the force of gravity on a 1kg object at the place the object is. The unit of gravitational field strength is the newton per kilogram (N/kg)
Question 13.
What is the equation for weight?
Answer 13.
Weight = mass x gravitational field strength
(newtons,N) (kilograms,kg) x(newtons/kilogram,N/kg)
Question 14.
Explain terminal velocity, saying what it is and refering to graph shapes.
Answer 14.
Terminal Velocity is when an object reaches a constant velocity as the drag force is equal and opposite to its weight. At terminal velocity, both the resultant force and acceleration are zero. On a graph you can tell when an object has reached terminal velocity because it flattens out.
Question 15.
What value (approximately) is the Earth's gravitational field strength at its surface?
Answer 15.
About 10N
Question 16.
If an object falls freely, what (approximately) is its acceleration?
Answer 16.
Acceleration = resultant force/mass
= 10N (force of gravity) / 1kg
= 10m/s squared
Question 17.
Does the acceleration of an object increase or decrease as it falls through a fluid, and why?
Answer 17.
Decreases, because the drag force increases and consequently the resultant force on it decreases.
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