Transcript 180 m/s 2
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: 5.0sin32 = 2.6 32 5.0cos32 = 4.2 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 Theory Assuming 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? FIRST : x vi (cos )t NEXT : y vi (sin )t 12 g (t ) 2 solve for t solve for y 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? 0J That’s a lot of WORK A 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)? PEelastic kx 1 2 2 distance spring is stretched or compressed 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 It’s the Law 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 Don’t get Dizzy! 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 On your marks, get set, GO Fifteen seconds after starting from rest, a car is going 30 m/s. What is the car’s acceleration? 2 m/s2 Jenny Craig says: A block of ice has a mass of 16 g. How much does the block weigh? 0.16 N Don’t get Dizzy! 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 The gravity of the situation 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 Momentum 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 v V = 2 m/s