11C Physics Past Paper PDF

Section 11C: Changing Motion 11C Questions Ø Ø Ø How do we describe motion if velocity changes? How does circular motion differ from linear motion? What causes projectiles to follow a curved path? pp. 261–264 What is acceleration? Section 11.8 acceleration (a) the rate of change in velocit...

Section 11C: Changing Motion 11C Questions Ø Ø Ø How do we describe motion if velocity changes? How does circular motion differ from linear motion? What causes projectiles to follow a curved path? pp. 261–264 What is acceleration? Section 11.8 acceleration (a) the rate of change in velocity Δv a = Δt The units for acceleration are m/s2. EXAMPLE 11-7 Calculating Acceleration from Velocity and Time At the end of a race, a top fuel dragster accelerates from 147 m/s west to 119 m/s west in 3.1 s. What is the acceleration of the car? p. 262 EXAMPLE 11-7 Calculating Acceleration from Velocity and Time At the end of a race, a top fuel dragster accelerates from 147 m/s west to 119 m/s west in 3.1 s. What is the acceleration of the car? Write what you know. vi = 147 m/s west vf = 119 m/s west Δt = 3.1 s vf − vi = 119 m/s − 147 m/s = a = ? a = Δv = Δt 3.1 s Δt m –9.0 2 or 9.0 m/s2 to the east s p. 262 EXAMPLE 11-8 Calculating Velocity from Acceleration and Time A bus is traveling down the road at 12.4 m/s. If it accelerates at 5.1 m/s2 for 2.7 s, what is its new velocity? p. 262 EXAMPLE 11-8 Calculating Velocity from Acceleration and Time A bus is traveling down the road at 12.4 m/s. If it accelerates at 5.1 m/s2 for 2.7 s, what is its new velocity? Write what you know. vi = 12.4 m/s a = 5.1 m/s2 Δt = 2.7 s vf = ? vf − vi a = Δv = Δt Δt è vf = aΔt + vi m m vf = (2.7 2 )(5.1 s) + 12.4 s s m = 26 s p. 262 Practice 1) What is the acceleration of a dog which increases its velocity by 3.0 m/s East over 1.5 seconds? p. 262 Practice 1) What is the acceleration of a dog which increases its velocity by 3.0 m/s East over 1.5 seconds? Given: Δv = 3.0 m/s Unknown: a = ? Δt = 1.5 s 3.0 m/s = 2.0 m/s2 a = Δv = Δt 1.5 s Practice 2) What is the acceleration of a dog, running at 6.0 m/s, that comes to a stop in 0.5 seconds? p. 262 Practice 2) What is the acceleration of a dog, running at 6.0 m/s, that comes to a stop in 0.5 seconds? Given: vi = 6.0 m/s Unknown: a = ? vf − vi a = Δv = Δt Δt vf =0 m/s Δt = 0.5 s − 6.0 m/s = 12 m/s2 = 0 m/s0.5 s p. 262 Practice 3) A dog has an initial velocity of 3.0 m/s. The dog sees a cat and accelerates at 4.0 m/s2 for 0.50 seconds as it chases the cat up a tree. What is the dog’s final velocity? p. 262 Practice 3) A dog has an initial velocity of 3.0 m/s. The dog sees a cat and accelerates at 4.0 m/s2 for 0.50 seconds as it chases the cat up a tree. What is the dog’s final velocity? Given: vi = 3.0 m/s Unknown: vf = ? vf − vi a = Δv = Δt Δt a = 4.0 m/s2 Δt = 0.50 s vf = aΔt+ vi m m m vf = (4.0 2 )(0.50 s) + 3.0 = 5.0 toward the tree s s s p. 262 Practice 4) The SpaceX Falcon Heavy on page 261 accelerates from launch to 78,000 m/s in 561 s. What is its acceleration? p. 262 Practice 4) The SpaceX Falcon Heavy on page 261 accelerates from launch to 78,000 m/s in 561 s. What is its acceleration? Given: vi = 0 m/s Unknown: a = ? vf = 78 000 m/s Δt = 561 s vf − vi = 78 000 m/s − 0 m/s = 139 m/s2 upward a = Δv = Δt Δt 561 s p. 262 Practice 5) A boat is moving at 27.5 m/s south and accelerates at 2.51 m/s2 north for 12.1 s. What is its velocity after it accelerates? Given: vi = 27.5 m/s south a = 2.51 m/s2 north = –2.51 m/s2 south Δt = 12.1 s Unknown: vf = ? vf − vi a = Δv = Δt Δt vf = aΔt+ vi vf = (–2.51 m/s2 )(12.1 s) + 27.5 m/s = –2.9 m/s south vf = 2.9 m/s north p. 262 free fall the motion of an object that falls due to gravity alone with no other forces acting on it The acceleration of a body, near the surface of the earth, in free fall is approximately 9.81 m/s2 The symbol for free fall due to gravity is g. free fall Free fall acceleration is not affecting by the mass of the object. Therefore, objects of different masses fall at the same rate. The free fall acceleration is affecting by the gravity system the objects are in. Therefore, objects on the moon fall with a lower acceleration than they would on Earth. Free Fall Graphs Practice 1) If an object falls from rest, how fast is it traveling after 5.0 s? (Look at the paragraph about free fall on page 262 and extrapolate to 5.0 s) p. 262 Practice 1) If an object falls from rest, how fast is it traveling after 5.0 s? (Look at the paragraph about free fall on page 262 and extrapolate to 5.0 s) Given: vi = 0 m/s Unknown: vf = ? a = 9.81 m/s2 vf = aΔt + vi = (9.81 m/s2)(5.0 s) + 0 m/s = 49.05 m/s Δt = 5.0 s time (s) velocity (m/s) 1.0 s 9.81 m/s 2.0 s 19.62 m/s 3.0 s 29.43 m/s 4.0 s 38.24 m/s 5.0 s 49.05 m/s p. 262 Practice 2) If an object started from rest, what was the object’s average velocity over the 5.0 s? p. 262 Practice 2) If an object started from rest, what was the object’s average velocity over the 5.0 s? Given: vi = 0 m/s vf = 49.05 m/s vavg = vi %vf 0 m/s + 49.05 m/s & = & = 24.52 m/s or 25 m/s with SF p. 262 How is twodimensional motion different from linear motion? Section 11.9 circular motion movement along a circular path Circular Motion centripetal acceleration acceleration that causes an object to move along a circular path projectile motion the two-dimensional motion of any flying object whose path is determined by the influence of an external force only, such as gravity trajectory the curved path of a projectile This path is the combination of constant velocity motion in the horizontal direction and accelerated motion in the vertical direction. Parabolic Trajectory