Speed, Distance and Time
Is speed a vector or scalar quantity?
Scalar
What is Newton's Third Law?
Every action has an equal and opposite reaction.
What does the dv/dt of a velocity-time graph represent?
Acceleration
What is net force?
The total amount of force acting upon an object
A 1200 W heater runs for 3 hours. How much energy does it use in kilowatt-hours (kWh)?
3.6 kWh
What is instantaneous speed?
The speed of an object at a specific point in time.
Two blocks of masses m=3kg and m=2kg are in contact on a frictionless horizontal surface. A horizontal force F=15N is applied to the 3kg block, pushing it against the 2kg block. What is the acceleration of the system?
9m/s2
What does the velocity-time graph look like when someone T-bones a car. Describe the graph.
Straight horizontal line, then sudden drop
If a bookshelf weighs 200 newtons, and there is a normal force of 30 newtons, what will happen?
The bookshelf will break with a downwards force of 170N
An old refrigerator uses 900 kWh per year, while a new energy-efficient model uses 450 kWh per year. If electricity costs $0.35/kWh, how much money would be saved each year by using the new refrigerator?
$157.50 per year
Convert km/h into m/s
divide by 3.6
True or False: A book resting on a table experiences a pair of equal and opposite forces consisting of gravity pulling down and the surface pushing up. These two forces form a Newton's Third Law action-reaction pair.
False
Someone eats 1,000 g of cheese. Since she's lactose intolerant, she immediately gets explosive diarrhea and is launched off the toilet. For every gram of cheese Tilly eats, her speed increases by 0.1 m/s. The diarrhea lasts for 105 seconds, during which she travels at this constant speed. How far does Tilly travel, and what would her distance–time graph look like?
10500m / 10.5km, Her distance-time graph would be a straight line starting at (0, 0) with a gradient of 100 m/s.
If a UFO is flying to earth with a force of 1 million newtons, and the air resistance typically is a half of the total force, calculate the net force.
1 million newtons up, because there’s no air resistance in space
A television has an efficiency of 25%. If the TV consumes 800 J of electrical energy, how much energy is wasted as heat?
600 J wasted
Which car is travelling faster if the speed of car A is 10m/s and car B is 35km/h?
Car A (36km/h)
An elevator goes downwards with an acceleration of 2.5m/s2. A person has a mass of m=60kg. What does the scale read?
438N
In a distance-time graph, describe the motion if the graph resembles a circle.
Time Travel
An object accelerates with a vector of 2m/s2 in the x-direction and 5m/s2 in the y-direction. What is the net force vector?
5.38m/s2
A household replaces ten 60 W incandescent bulbs with ten 9 W LED bulbs. If the lights are used for 5 hours each day, how much electrical energy is saved in one month (30 days)?
76.5 kWh
Two trains start 300km apart. They travel towards each other. Train A travels at 40km/h and train B travels at 60km/h. How many hours until they meet?
3 hours
If you suddenly double the pulling force F, what must happen to the block's acceleration?
x2
Someone is moving at an accelerated rate. Find the distance travelled from 2 to 5 seconds if the graph of the person's velocity is described by the equation v=5t2
195 units
How do you calculate the net force on a rocket that continuously expels mass, where F = dp/dt expands into both mass changes and velocity changes?
M(dv/dt) = f+v(dm/dt)
An air conditioner has an input power of 2000 W and a useful cooling output of 7000 W. Another model has an input power of 1500 W and a useful cooling output of 6000 W. Which model is more energy efficient and by what percentage points?
Model 2 is more efficient.
Model 1 efficiency = 350%
Model 2 efficiency = 400%