PHY 101 Lecture Notes - Lecture 9: Flickr, Terminal Velocity

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20 May 2018

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Distance (d)

it is the number of metres (m) between two points or the metres travelled by an object

Time (t)

the number of seconds it takes for an event to occur

Acceleration (a)

the rate that speed changes for a moving object, a change in speed : getting faster or slower (ms-2)

-is an increase in speed in a certain time

-can be calculated by dividing the change in speed by the change in time, a=v/t

Deceleration

a word used for 'slowing down' or 'negative acceleration' (-ms-2)

-when describing in word answer NEVER say 'it is decelerating at -10m/s2

-deceleration:write using positive value eg- decelerating at 10m/s2

-deceleration with a negative value: eg- accelerating at -10m/s2

Mass (m)

the quantity of matter in an object measured in kilograms (kg)

Weight force

is a force measured in Newtons and it is the force due to gravity. Fw=mg

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Work (w)

is the energy transferred from one form to another and is work is done whenever an object moves in

the direction of the force that is being applied to it, measured in joules (J)

-If you are carrying something "along" there are NO forces acting on it in the direction of motion (no

change in speed so no change in energy) so no work is done.

Power (P)

the rate at which work is being done measured in Watts (W)

-work done per second

-A more powerful person/thing does more work in the same time or the same work in less time

Pressure (P)

pressure depends on the amount of force used and how big an area of force is spread over or force

applied to a certain area measured in (Nm-2) or Pascals (Pa)

-is force per unit area

-To turn cm2 into m2 divide by 10,000 (100 x 100) 10^-3

Force (F)

a push or pull measured in Newtons (N)

something that can make an object either speed up, slow down, stop, changes its direction or shape, to

work out F=ma

Gravity

is a force that attracts objects towards the centre of the earth, g=10Nkg-1

How to solve physics problems?

-read question carefully

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-write equation/formula

-substitute in numbers

-rearrange

-calculate

-correct unit ( make sure to make any conversions if needed)

Stationary

if something is not moving, it is said to be stopped or stationary

What is the symbol for change in?

TRIANGLE

Constant Speed

if a object is moving at a 'constant speed' then it is covering equal distances in equal time

Average Speed

total distance travelled / total time taken

Distance/Time Graphs

-distance an object has moved at different times can be plotted on this graph

-vertical axis (y) is used for distance

-horizontal axis (x) is used for time

-size of slope (gradient) of the graph gives the velocity/speed

-flat sections are where object has stopped

-the greater the slope the greater the speed.

-curves represent acceleration or deceleration

-steep curve means it's speeding up

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Document Summary

Distance (d) it is the number of metres (m) between two points or the metres travelled by an object. Time (t) the number of seconds it takes for an event to occur. Acceleration (a) the rate that speed changes for a moving object, a change in speed : getting faster or slower (ms-2) Is an increase in speed in a certain time. Can be calculated by dividing the change in speed by the change in time, a=v/t. Deceleration a word used for "slowing down" or "negative acceleration" (-ms-2) When describing in word answer never say "it is decelerating at -10m/s2. Deceleration:write using positive value eg- decelerating at 10m/s2. Deceleration with a negative value: eg- accelerating at -10m/s2. Mass (m) the quantity of matter in an object measured in kilograms (kg) Weight force is a force measured in newtons and it is the force due to gravity.

Related Questions

You push an object, initially at rest, across a frictionless floor with a constant force F for a time interval ?t, resulting in a final speed of v for the object. You repeat the experiment, but with a force that is twice as large, 2F. What time interval is now required to reach the same final speed v? Hint: is acceleration different for the second case? Is it larger or smaller than in the first case? Use Newton's 2nd law: a = Fnet/m.

Galileo thought about whether acceleration should be defined as the rate of change of velocity over time or as the rate of change in velocity over distance. He chose the former, so let’s use the name “vroomosity” for the rate of change of velocity over distance. For the motion of a particle on a straight line with constant acceleration, the equation v = v_i + at gives its velocity v as a function of time. Similarly, for a particle’s linear motion with constant vroomosity k, the equation v = v_i + kx gives the velocity as a function of the position x if the particle’s speed is v_i at x = 0. (a) Find the law describing the total force acting on this object of mass m. Describe an example of such a motion or explain why it is unrealistic for (b) the possibility of k positive and (c) the possibility of k negative.

violethorse873

Question 1 of 7 0.5 Points
A 6 N force acts on a 0.3-kg object for 0.3 seconds. By how muchdoes the object's momentum change (in kg-m/s)?

Question 2 of 7 0.5 Points
A 0.4-kg object is traveling to the right (in the positivedirection) with a speed of 1 m/s. After a 0.2 s collision, theobject is traveling to the left at 3 m/s. What is the magnitude ofthe impulse (in N-s) acting on the object? The answer must bepositive.

Question 3 of 7 1.0 Points
The force shown in the attached figure is the net eastward forceacting on a ball. The force starts rising at t = 0.020 s, fallsback to zero at t = 0.062 s, and reaches a maximum force of 55 N atthe peak. Determine with an error no bigger than 25% (high or low)the magnitude of the impulse (in N-s) delivered to the ball. Hint:Do not use J = F?t. Look at the figure. Find the area of a nearlyequally sized triangle.

Question 4 of 7 1.0 Points
A bat hits a moving baseball. If the bat delivers a net eastwardimpulse of 0.6 N-s and the ball starts with an initial horizontalvelocity of 3.8 m/s to the west and leaves with a 5.2m/s velocityto the east, what is the mass of the ball (in grams)?
Part 5 of 7 -

Question 5 of 7 0.5 Points
The force sensor measures the force on the sensor due to thebumper, but the cart's momentum change arises from the force on thecart due to the bumper. Which of the following facts are needed toassert that the magnitude of these two forces are nearly equal atall times.
1. Their magnitudes differ by the magnitude of the net force on thebumper.
2. The force of friction is small.
3. The net force on the bumper is small.
4. The cart's weight is canceled by the the normal force exerted bythe track.

A. 1, 3

B. 2, 4

C. 3, 4

D. 1, 2

E. 1, 4

F. 1, 2, 3, 4

G. 2, 3

Part 6 of 7 -

Question 6 of 7 1.0 Points
A cart traveling at 0.3 m/s collides with stationary object. Afterthe collision, the cart rebounds in the opposite direction. Thesame cart again traveling at 0.3 m/s collides with a differentstationary object. This time the cart is at rest after thecollision. In which collision is the impulse on the cartgreater?

A. The second collision.

B. Cannot be determined without knowing the mass of the cart.

C. The impulses are the same.

D. The first collision.

E. Cannot be determined without knowing the rebound speed of thefirst collision. Reset Selection

Part 7 of 7 -

Question 7 of 7 0.5 Points
The force vs. time graphs for two collisions are shown. Whichcollision has the largest impulse?

A. The impulse for collision 2 since it lasts longer.

B. Cannot be determined since the masses are unknown.

C. The impulse for collision 1 since it has the larger maximumforce.

D. Cannot be determined since the initial an final speeds areunknown.

E. The impulses are the same.

PHY 101 Lecture Notes - Lecture 9: Flickr, Terminal Velocity

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