U1 template Flashcards
1
Q
Use Newton’s third law to explain
A
- “A” exerts a force on “B”
- By N3, “B” exerts an equal and opposite force on “A”
- “XX” force is greater than “YY”
- Resultant force on “A”
- By N2, F=ma, “A” will accelerate
(if terminal velocity) - speed increases until forces are balanced
- By N1, resultant force equals to zero, acceleration equals to zero
2
Q
Why accelerate/decelerate
A
- “A” exerts a force on “B”
- By N3, “B” exerts an equal and opposite force on “A”
- “XX” force is greater than “YY”
- There is a resultant force on “A”
- By N2, F=ma, “A” will accelerate
3
Q
Why the forces are not Newton’s third law pair
A
- Forces of equal magnitude that act in opposite directions
- Same type of force
- Acting on different bodies
- (explain which part is incorrect)
- One force is “Type A” force, the other is “Type B” force
4
Q
Effect of motion to air resistance
A
- Air resistance act to oppose the motion of “object”
- So it decreases the time for which the “object” is in the air
- Vertical velocity is reduced
- Vertical distance is reduced
- Horizontal velocity is reduced
- Horizontal distance is reduced
5
Q
Energy/Work done conversion, energy is less OR Why theoretically potential energy and actual potential energy is different
A
- some energy / work done was not transferred to “YYY”
- external forces act on “XXX”
- work done by force (friction/resistance) transfer to thermal energy
- velocity / kinetic energy is less
6
Q
Momentum zero but two objects move to opposite sides
A
- Initial momentum is zero
- Due to conservation of momentum, the total momentum before “XXX” = total momentum after “XXX” so final momentum is zero
- momentum of “object A” is equal to the momentum of the “object”
- The momentum of “object A” is opposite in direction to the momentum of “object B”
- As the mass if “object A” is greater, the velocity of “object A” will be lower
7
Q
Stoke’s Law
A
laminar flow, small sphere object, low speed
8
Q
Why float
A
- there is an upthrust which is equal to the weight of water displaced
- upthrust is equal to the weight of the “object” when it is partially submerged
9
Q
Why sink
A
- upthrust is less than the weight of “object”
- resultant force acts downwards on the “object”
- “object” will sink
10
Q
Terminal velocity
A
- initially there is a force A. There is an upward/downward force
- it accelerates
- drag / air resistance increases as velocity increases (or vice versa)
- resultant force decreases, acceleration decreases
- until resultant force is zero
- it moves with terminal velocity
11
Q
Terminal velocity experiment
A
- Place two or more rubber bands on the cylinder
- Top band should be far enough below the surface for terminal velocity to be reached
- Measure time for the sphere to fall a given distance using the stopwatch and measure the distance fallen using a meter ruler
- Repeat measurements at least for 5 times and take averages
- Terminal velocity = distance between markers / average time between markers
- Measure the times for different distances
- terminal velocity = gradient of graph of distance against time
12
Q
Relationship between large sphere, viscosity, drag, velocity and temperature
A
- larger diameter, larger drag force
- lower temperature, more viscous
- greater viscosity, larger drag force
- larger drag force, lower velocity
13
Q
Greater the length of a rope, smaller the stiffness
A
- greater the length of the rope, greater the extension for a given force
- stiffness k = F / x so stiffness decreases
14
Q
Find diameter of a sphere
A
- Using a micrometer
- Take multiple readings at different orientations
- Calculate the mean
15
Q
Use graphic method
A
- Use “AAA” to measure “object”
- Repeat experiment for at least 5 sets of measurements with different “length / time…”
- Plot a graph of “YYY” on the y axis and “XXX” on the x axis
- Measure the gradient
- Gradient is “BBB”
