Chapter 2 - Mechanics Flashcards
What is an instantaneous value?
It’s a value at one particular time
Instantaneous speed is also the same as velocity
How do you work out relative velocities?
By Simple addition or subtraction as appropriate.
Features of a displacement-time graph
The gradient is equal to the velocity
Features of a velocity-time graph
The gradient is equal to the acceleration
The area under the graph is the displacement
Features in a Acceleration-time graph
The area under the graph is the change in velocity
How do you use light gates to measure acceleration?
It’s a device that senses and records the time of when an object cuts through a beam of light. Use the length of the object that breaks the beam, the average speed can be calculated.
How do you use strobe photography to measure acceleration?
It gives out brief flashes of light at fixed time intervals. Use the camera and if it’s the only source of light, pictures will have captured the objects motion.
How do you use ticker timer to measure acceleration?
It has dots on a strip of paper at regular time intervals. (Normally every 1/5 of a second). Attach it to the object and let it fall. The length of the paper and time are then used.
What is the condition needed to use the SUVAT equations?
Constant acceleration
What does the U and the V stand for in the SUVAT equations?
U - initial velocity
V - final velocity
What does it mean if an objects in free-fall?
When we can ignore the effects of air resistance and the object is falling in a uniform gravitational field.
What’s the shape of projectile motion?
Parabola
What are the only forces acting during a projectile motion?
Gravity and friction. In many situations air resistance can be ignored
What are the components of projectile motion?
The vertical and horizontal motion are independent of one another - assuming the gravitational force is constant.
Horizontal component to projectile motion?
There are no forces in this direction, there is no horizontal acceleration. So the velocity in this direction must be constant
Vertical component in projectile motion
There’s a constant vertical force downwards of 9.81/ 10 ms^-2,
so there is constant vertical acceleration.
What’s the method to solve any problem of projectile motion?
1) . Use angle of launch to resolve initial velocity into components
2) . Use vertical component of velocity to determine time of flight
3) . Use the horizontal component and time of flight for the range
4) . Use vector addition to solve for velocity at any point
If there is a given speed, what angle of launch is needed for the greatest range?
45 degrees
What will happen if 2 objects are released together, one from rest and the other one already with a horizontal velocity?
They will both hit the ground together because the forces pulling them down are the same.
What happens when an object moves through a fluid?
There will be frictional fluid resistance e.g terminal velocity
It can also be called viscous drag
What factors effect the drag force on an object?
Relative velocity of the object with respect to the fluid
Shape and size of the object
The fluid used
What happens to the projectile motion of an object when fluid resistance is taken into account?
The vertical and horizontal components of velocity will both be reduced, thus the path the object takes will be smaller.
What is force?
The cause of a deformation or a velocity change
What’s the effect of a resultant force?
A change in velocity, thus acceleration.
If the resultant force is zero then velocity is constant
