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Subterm 1
Topics
• Motion in 1 direction
• Motion in 2 directions
• Force and Newton’s Laws
• Energy and Momentum
Vectors
Resolve the vector below into it’s rectangular components:
5.0cos32 = 4.2
32
5.0sin32
= 2.6 5.0
Vectors
A truck drives up a hill with a horizontal velocity component of 21 m/s and vertical component of 5.7 m/s. What is the resultant velocity of the truck (speed and angle of incline above the horizontal)?
22 m/s at a 15 incline
Projectile TheoryAssuming air resistance is negligible, what happens to the horizontal velocity of a projectile after it is released?
A. velocity increases
B. velocity decreases
C. velocity remains constant
C (Newton’s First Law)
Projectiles Launched Horizontally
A pelican flying along a horizontal path drops a fish from a height of 5.4 m while traveling 5.0 m/s. How far does the fish travel horizontally before it hits the water below?
5.3 m
Projectiles Launched at an Angle What formula or set of formulas would you use to solve the word problem below?
A firefighter 50.0 m away from a burning building directs a stream of water from a fire hose at an angle of 30.0 above the horizontal. If the velocity of the stream is 40.0 m/s, at what height will the stream of water strike the building?
y tgtvy
tvx
i
for solve )()(sin :NEXT
for t solve )(cos:FIRST2
21
i
Projectiles Launched at an Angle
Solve: A stone is thrown at an angle of 30.0 above the horizontal from the top edge of a cliff with an initial speed of 12 m/s. A stopwatch measures the stone’s trajectory time from the top of the cliff to the bottom at 5.6 s. What is the height of the cliff?
120 m
That’s a lot of WORK
A child moving at constant velocity carries a 2 N ice-cream cone 3 m across a level surface. What is the net work done on the ice-cream cone?
0 J
That’s a lot of WORKA horizontal force of 200 N is applied to move a 55 kg television set across a .01 km long surface. What is the work done by the 200 N force on the television set?
2000 J
I just don’t have the ENERGY
A 3.50-kg rubber chicken flying through the air has a kinetic energy of 4586 J. What is the velocity of the rubber chicken?
51.2 m/s
Its SPRINGtime
In the formula for springs below, what does “x” represent (be specific)?
distance spring is stretched or compressed
221 kxPEelastic
Its SPRINGtime
The staples inside a stapler are kept in place by a spring with a relaxed length of 0.115 m. If the spring constant is 51 N/m, how much elastic potential energy is stored in the spring when its length is 0.150 m?
0.031 J
You’ve got POTENTIAL
A 500. N crate is at the top of a 5.00 m long ramp, which is inclined at 20.0° with the horizontal. What is its potential energy?
855 J
A cannonball is fired into space with a force of 10 N. How much force is needed to keep the cannonball moving in frictionless space?
Zero Newtons
It’s the Law
A 2000 kg car experiences a 400 N force from air resistance. What must the force of the engine be to accelerate the car at a constant 3.0 m/s2?
6,400 N
It’s the Law
A car rounds a curve at a constant speed. Is there a net force on the car? And if so, in what direction is it?
Yes; towards the center of the curve
Don’t get Dizzy!
Fifteen seconds after starting from rest, a car is going 30 m/s. What is the car’s acceleration?
2 m/s2
On your marks, get set, GO
A block of ice has a mass of 16 g. How much does the block weigh?
0.16 N
Jenny Craig says:
A car is negotiating a flat curve of radius of 50.0 m with a speed of 20.0 m/s. The centripetal force provided by friction is 1.20 x 104 N. What is the mass of the car?
1,500 kg
Don’t get Dizzy!
What is the centripetal acceleration of a point on the perimeter of a bicycle wheel of diameter 70.0 cm when the bike is moving 8.0 m/s?
180 m/s2
Don’t get Dizzy!
A satellite is in circular orbit 230 km above the surface of the earth. It is observed to have a period of 89.0 min. From this information, calculate the mass of the earth. (the mean radius of the earth is 6.38 x 106 m)
6.0 x 1024 kg
The gravity of the situation
Two identical freight cars roll without friction towards each other on a level track. One rolls at 5.0 m/s and the other rolls at 2.0 m/s. After the cars collide, they couple and roll together. What is the new speed of the coupled cars?
1.5 m/s
Momentum
A 150g baseball reaches a batter with a speed of 25 m/s. After it has been struck, it leaves the bat at 35 m/s in the opposite direction. If the ball was in contact with the bat for .001 s, find the average force exerted on it during this period.
25
35
F t = mv
= mv final – mv initial
F (.001 sec) = (.150kg)(35m/s)-(.150)(-25)
F = 9000N
Momentum
A 30 kg girl who is running at 3 m/s jumps on a stationary 10 kg sled on a frozen lake. How fast does the sled then move?
Mgvg + msvs = (mg+ms)vgs
90 kg m/s + 0 = 40 vV = 2 m/s
Momentum