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Acceleration of gravity
Unit Circle
Vectors
Kinematics 1 dimension
Wild Cards
100
What is the acceleration of gravity a) when you throw an object b) as the object reaches the top c) when the object falls back in your hand
a)-9.8 m/s^2, b)-9.8 m/s^2, c) -9.8 m/s^2 It does not matter where an object that is in the air is. The acceleration of gravity is always 9.8m/s^2 as long as we are on earth. :)
100
What is the sin of 60 (decimals)
0.87
100
Is Speed a scalar or a vector? and why
Speed is a scalar because it has magnitude but no direction. Magnitude is the numerical answer. Ex: 50 mph (vectors are quantities that have magnitude and also direction. Ex 50 mph north)
100
The formula V=d/t can only be used if....
A/ The velocity is constant; there is no acceleration (you can assume that there is not acceleration if the problem does not imply that the velocity is changing. So nothing is speeding up or slowing down or changing direction)
100
Which one falls faster a bowling ball or a basket ball and why
They fall at the same time. BECAUSE F=m.a or Fg=m.g The force of gravity is our weight. The bigger the weight the bigger the mass so that the acceleration of gravity equals 9.8m/s^2. The lower the weight (Fg) the lower the mass, so that the acceleration of gravity equals 9.8m/s^2. This is better explained in the kinematics ppt
200
Assuming the acceleration of gravity is -10m/s^2. What is the velocity of an object 5 seconds after I drop it
-50m/s ( you should not need to calculate) As I open my hands and the object drops. The velocity will go from: t=0 v=0m/s t=1 v=-10m/s t=2 v=-20m/s t=3 v=-30m/s (the sign just says the direction since we chose down , west and south to be negative)
200
What is the tangent of 360 degrees
tan = sin/cos = Y/X = 0/1= 0
200
A truck that is carrying a film crew must be driven at the correct velocity to enable the crew to film the underside of a biplane flying at an angle of 35o to the ground at a speed of 95 km/h. What is the trucks velocity? variables, formula (s), sketch
V=95kph (this is the resultant velocity) tetha= 35 degrees Solve Vx = V cos(tetha) Vx = 95km cos(35o)? h Vx = 78km? h
200
a) What does constant acceleration mean? b) What does 1 dimension mean?
A/ a) velocity increases by the exact same amount every second b) that you are moving along the X axis or the Y axis but not both. You do not move at an angle.
200
What is the velocity of an object the instant that you open your hand to drop it?
What is 0 m/s
300
If I throw an object up with a velocity of 50m/s. What is the velocity of the object 5 seconds after I throw it. (assume g=-10m/s^2) Challenge: What is the velocity 7 seconds after I throw it?
A: 0m/s A: challenge = -20m/s Vo=50 V=? d=@; a=-10m/s^2; t=7s V=at+Vo V=(-10)(7)+50 V=-20m/s
300
What is the tangent of 90 degrees
tangent = sin/cos = Y/X = 1/0 = undefined
300
A telephone pole support cable is in the way of some construction workers. In order for the work to proceed, the cable must be moved 2m closer to the pole. If the pole is 10m tall and the cable is currently fastened to the ground 8m from the pole, how much will the workers need to cut off from the cable when they move it? (PSYW)
What is 1.1 m (answer on vector ppt)
300
When is acceleration positive?
When you move forwards and the speed increases When you move backwards and the speed decreases (hint: use hand game same are + and opposite are -)
300
If I throw a ball up with 5 m/s and I throw a ball down with 5m/s. a) which ball will strike the grown with a higher velocity? b) which ball will take longer to fall? (SKETCH and illustrate why by labeling velocities along the path.)
a: They both strike the ground with the same velocity. b: The one that I throw up takes longer to fall. (as the ball that I threw up passes by my hand again it has the same velocity that I used to throw it up but in the negative direction)
400
If I throw an object with 50m/s up. (Assume g=-10m/s^2; SKETCH) a) What is the velocity of the object when it falls back in my hand? b) What is the velocity of the object 7 seconds after I throw it up.
a) -50 m/s b) -20 m/s
400
A kangaroo is capable of jumping to a height of 2.62 m. Determine the takeoff speed of the kangaroo.
A: Vo=7.17 m/s V^2 = 2ad +Vo^2 (0 m/s)2 = + 2(-9.8 m/s2)(2.62 m)+Vo^2 0 = - 51.35 m2/s2 +Vo^2 51.35 = Vo^2 Vo = 7.17 m/s
400
A boat that moves with a constant velocity of 12 m/s is moving on a river with a constant current of 4 m/s. What is the resultant velocity of the boat if: a) The boat is traveling to the north and the current is to the south? b) The boat is traveling to the south and the current is to the south? c) The boat travels to the east, across the current, while the current is to the south?
a) 8m/s b) -16m/s c)sqr(12^2 +4^2) vb=12m/s Vc=4m/s
400
DRAW the position vs time graphs (2) and the velocity vs time graph (2) that show: Decreasing velocity at a constant rate (hint: it can decrease moving forward or backwards)
Position vs time: You should see arcs that end with a hill (slope of zero) Velocity vs time: You should see straight lines that meet at 0m/s
400
A ball is thrown off a building. If the ball is thrown up at 5m/s and lands 3s later. PSYW a)What is the height of the building? b) Find the impact velocity of the ball? ( the second it hits the ground, not a sec later.)
a) -29.1 m b) -24.4 m/s down
500
a) If I drop a hair could it be subject to free fall? b) Does the force of gravity affect you when you reach terminal velocity?
a) NO because free fall is when the force of gravity is the only force that affects the fall of the object. A hair will be affected significantly by drag from the air. b) YES, terminal velocity is the velocity that we reach when the force of gravity = Drag force. After that there is no net force that causes an object to fall so the object will no longer accelerate and it will strike the ground at that speed. Since a force does not cause the object to fall. The reason that the object falls is innertia
500
If Michael Jordan has a vertical leap of 1.29 m, then what is his takeoff speed and his hang time (total time to move upwards to the peak and then return to the ground)?
A: Vo = 5.03 m/s; hang time=1.03 s V^2 = 2ad + Vo^2 (0 m/s)2 = 2(-9.8 m/s2)(1.29 m)+ Vo^2 Vo = 5.03 m/s To find hang time, find the time to the peak and then double it. V=at+Vo 0 m/s = (-9.8 m/s2)*tup + 5.03 m/s tup = 0.513 s hang time =2*0.513= 1.03 s
500
A football player runs directly down the field for 20 m before turning to the right at an angle of 25o from his original direction and running an additional 15 meters. Then he runs 30m at an angle of 65o NE before getting tackled. What is the magnitude and direction of the runner’s total displacement?
What is 49 meters @22 degrees North of East. Answer on vector PPT
500
A park ranger driving on a back country road suddenly sees a deer “frozen” in the headlights. The ranger who is driving at 11.4 m/s, immediately applies the brakes and slows with an acceleration of 3.8 m/s2. If the deer is 20m from the ranger’s vehicle when the brakes are applied, how close does the ranger come to hitting the deer? How much time is needed for the ranger’s vehicle to stop? PSYW
A/ 1.5 m 3.0 seconds Vo=11.4m/s V=0m/s d=? a=-3.8 m/s^2; t=@ V=2ad+Vo^2 d=18.5m 20-18.5=1.5m. Then use any equation to find time
500
A person standing on the edge of a high cliff throws a rock straight up with an initial velocity of 13.0 m/s. The rock misses the edge of the cliff as it falls back to earth. Calculate the position and velocity of the rock a)1.00 s, b)2.00 s, and c) 3.00 s after it is thrown, neglecting the effects of air resistance
a) d =8.10 m ; vf =+3.2 m/s b) please check ppt for b and c. Be sure to understand what is happening at each point