subterm 1 topics motion in 1 direction motion in 2 directions force and newton’s laws energy and...

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