Physics Chapter 1&2 Review

Match the following units: one will be used twice Speed or Velocity kg Distance or displacement N Acceleration s Force m/s Mass m Weight cm/s2 Time

Match newton’s 3 laws of motion: Newton’s First Law Newton’s Second Law Newton’s Third Law For every force there is an equal but opposite reaction. Every object in motion stays in motion, or stays at rest, unless acted upon by an outside force. Increasing the force, increases the acceleration. a=f/m Also called the Law of Inertia . Answers: 1) b, e 2) c, d 3) a, f

Match the following: Terminal speed a. The amount of force required to accelerate a mass of 1 kg at a rate of 1 m/s² Free fall b. push or pull on an object Force c. rate of change in speed of an object. Inertia d. the area on a speed/time graph Weight e. related to ONLY mass Acceleration f. force of air resistance equals the force of gravity and object then falls at a constant speed Newton g. 9.8 m/s2 Acceleration due to gravity h. object is accelerating with no other forces acting upon it Distance i. mass times gravity

Answers F H B E I C A G D

Calculate the speed of the car if it travels 60meters in 10 seconds. V=x/t = 60/10 = 6 m/s

How far would a bird to travel at a speed of 2.0 m/s for 5 seconds? X= vt = 2.0 x 5 = 10 m

How long would it take a bowling ball to travel 20 m at 5.0 m/s? T = x/v =20/5.0 = 4 s

The car accelerates from 0 to 60 mph in 3 seconds The car accelerates from 0 to 60 mph in 3 seconds. Calculate the acceleration of the car in mph/s. A = v2-v1/t = 60-0 / 3 = 20 mph/s

The car slows from 40 m/s to 10 m/s in a school zone in 10 seconds The car slows from 40 m/s to 10 m/s in a school zone in 10 seconds. Calculate the acceleration of the car. A = 10 – 40 / 10 = -3m/s2

Slope of a position vs. time graph? = speed

Slope of a speed vs. time graph? = acceleration

What is the speed of the car during the interval from t=0 seconds to t=2.0 seconds? Slope = y2-y1 x2-x1 = 10-0 = 5m/s 2-0 Draw the speed/time graph from this position/time graph.

What is the speed at 3 seconds? What is the speed at 5 seconds? Use the line. At 3s = 4 m/s ; at 5s = 3 m/s What is the speed at 3 seconds? What is the speed at 5 seconds?

What is the acceleration of C-D? Where is the acceleration zero? Find slope = -1 B-C, D-E

What is the distance from A-E? A-B: (1/2)(1) (4) = 2 B-C: 3 x 4 = 12 C-D: the triangle: (1/2)(2)(2) = 2 the square: 2 x 2 = 4 D-E: 2 x 2 = 4 Then add up = 2+ 12 + 2 + 4 + 4 = 24 m Find area under line. Area of a triangle A=1/2bh Area of square A = l x w

Which segment has the greatest acceleration? A-B (most steep)

During which segment is the net force zero During which segment is the net force zero? (or no net force being applied) Where a = 0 B-C and D-E

Calculate the acceleration of the box: Subtract forces 8-2 = 6N

Calculate the force on a 10 kg box that accelerate due to the force at 2 m/s2. F = ma = (10)(2) = 20N

Calculate the acceleration of the boat if the motor propels the boat forward with 100 N of force, and the boat as a mass of 10 kg. A = F/m = 100N / 10kg = 10 m/s2

Calculate the mass of the object if it accelerates at 4 m/s2 as it is pulled by a force of 20 N. M = F/a = 20N / 4 = 5 kg

Inertia A golf ball has a mass of 0.05 kg, and the average bowling ball has a mass of 5 kg. Which requires more force to stop if they are rolled towards one another at the same speed over a certain amount of time? Objects with more mass have more inertia and are more resistant to changes in their motion.

Net Force To cause a Net Force – must have acceleration

Net Force The net force is what causes acceleration. If net force on object is zero then there is NO acceleration.

A brick is thrown off the top of a building A brick is thrown off the top of a building. If it fell for 10 seconds how tall is the building? Vf=(g)(t) OR y = (½) (g) (t2) vavg =V1 + V2 2 D=(vavg)(t) = (1/2) (9.8)(102) = 490 m

#1) How long would it take a penny to drop 200 meters? y = (½) (g) (t2) t = 200m √ (.5) (9.8) t = 6.39s #2) A brick is thrown off the top of a building. If it fell for 10 seconds how tall is the building? y = (½) (g) (t2)

The meteor reaches an instantaneous velocity of 98 m/s as it falls toward the earth. How long was it in free fall? Vf=(g)(t) T = v/g = 98m/s / 9.8 = 10s