Physics Name: ______

Physics Review

Motion and Forces

1. Newton's laws predict the motion of most objects. As a basis for understanding this concept:

a. Students know how to solve problems that involve constant speed and average speed.

b. Students know that when forces are balanced, no acceleration occurs; thus an object continues to move at a constant speed or stays at rest (Newton's first law).

c. Students know how to apply the law F = ma to solve one-dimensional motion problems that involve constant forces (Newton's second law).

d. Students know that when one object exerts a force on a second object, the second object always exerts a force of equal magnitude and in the opposite direction (Newton's third law).

e. Students know the relationship between the universal law of gravitation and the effect of gravity on an object at the surface of Earth.

f. Students know applying a force to an object perpendicular to the direction of its motion causes the object to change direction but not speed (e.g., Earth's gravitational force causes a satellite in a circular orbit to change direction but not speed).

g. Students know circular motion requires the application of a constant force directed toward the center of the circle.

Equations:

vavg = d/t = ½ ( vi + vf) Fnet = ma

v = v0 + at F = mv2/r

d = v0t + ½ a t2 F = G m1m2/r2

g = -9.8 m/s2 w = mg


Problems:

1.  A bus travels 30 km in ½ hour. What is its average speed in km/h?

2.  A cyclist travels for 15 minutes with an average speed of 10 km/h. How far does the cyclist travel?

3.  What is the acceleration of a bus that goes from rest to a speed of 25 m/s in 5 s?

4.  Find the maximum height attained by a ball thrown straight up with a speed of 30 m/s?

5.  An apple drops from a tree and hits the ground in 1.4s. How far does it fall?

6.  For problem #5, what is the speed just before it hits the ground?

7.  Calculate the resultant velocity of an airplane which normally flies at 100 km/h when it encounters a 10 km/h headwind. What happens when the wind is a 10 mph tailwind?

8.  For an object thrown upward, what is its speed at the top of its path?

What is its acceleration at the top of its path?

For a projectile, which component of speed stays constant?

Which component is affected by gravity?

What is the speed of the projectile at the top of its path?

What is its acceleration at the top of its path?

9.  What is the law of inertia? Does it apply to objects that are stationary or ones that are moving?

10.  If no force is required to maintain constant motion, why do we have to pedal to keep moving?

11.  What is the net force on an object that is at equilibrium?

12.  What is the weight of a car which has a mass of 1800 kg?

13.  What is the mass of a 100 N crate?

14.  What is the acceleration of a given to a 50 kg block of cement when it is pulled sideways with a force of 800 N? Draw a diagram for this problem.

15.  Heather can apply a force of 72 N to a wagon in which sits her litter brother. The brother and the wagon has a mass of 48 kg. If starting from rest, how much speed will the wagon pick up after Heather has pushed it for 3 s?

16.  A 500 kg car and a 1500 kg car is given equal acceleration. How much greater is the force that acts on the bigger car?

17.  Scarlet skydiver who has a mass of 60 kg, jumps from a stationary helicopter.

a)  What is the net force on her as she emerges from the helicopter?

b)  What is the net force on her when she reaches terminal speed?

c)  What is her acceleration?

18.  Skelly the child skater is propelled by rocket power. Skelly and the rocket together has a mass of 25 kg. When the thrusting force is 100 N, and the friction is 20N, what is Skelleys acceleration?

19.  Two people attempt a tug-of-war on low-friction ice. One person has four times the mass of the other. Relative to the acceleration of the heavier person, what will be the acceleration of the lighter person?

20.  If you hit a wall with a force of 200 N, how much force is exerted on you? State the law that you used for this.

21.  When you walk along the floor, what pushes you forward?

22.  How can a rocket be propelled above the atmosphere when there is no air to “push against”?

23.  When you whirl a can at the end of a string in a circular path, what is the direction of the force that acts on the can? What is the name given to it?

24.  How does the direction of motion of a satellite in circular orbit compare with the direction of the force on the satellite?

25.  If the mass of the Earth was increased with no change in radius, what would happen to your weight?

26.  If the radius of the Earth was doubled with no change in mass, what would happen to your weight?

27.  Why doesn’t the moon fall onto the Earth’s surface?

28.Describe the motion described by the following graphs. Draw velocity vs.time and acceleration vs. time graphs for each dist vs. time graph.

What is the slope of these graphs equal to? Label these two forces.


Calculate the net force.

Calculate the acceleration of the box. Calculate the force of friction, Ff.


Conservation of Energy and Momentum
2. The laws of conservation of energy and momentum provide a way to predict and describe the

movement of objects. As a basis for understanding this concept:

a. Students know how to calculate kinetic energy by using the formula E = (1/2)mv2.
b. Students know how to calculate changes in gravitational potential energy near Earth by using the formula (change in potential energy) = mgh (h is the change in the elevation).

c. Students know how to solve problems involving conservation of energy in simple systems, such as falling objects.

d. Students know how to calculate momentum as the product mv.
e. Students know momentum is a separately conserved quantity different from energy.

f. Students know an unbalanced force on an object produces a change in its momentum.

g. Students know how to solve problems involving elastic and inelastic collisions in one dimension by using the principles of conservation of momentum and energy.

Problems.

1.  Calculate the work done as a 100 N force pushes a crate 5 m along a factory floor.

2.  Calculate the increase in potential energy when a 50 N box is lifted a vertical distance of 3m.

3.  What is the increase in potential energy of a 50 kg box when it is lifted a distance of 5m.

4.  Calculate the kinetic energy of a 10 kg car traveling at 4 m/s.

5.  Calculate the power expended by a person who is carrying a 50 kg box 3 m high in 3 seconds.

6.  Calculate the change in kinetic energy when the speed of a 10 kg car increases form 4 m/s to 10 m/s.

7.  State the law of conservation of energy.

8.  A simple pendulum 1 m long has a 5 kg bob.

a)  When the pendulum in lifted from the vertical position to the horizontal position, what is the increase in potential energy of the bob?

b)  If the pendulum is then released, what will be the speed of the bob as it moves through the lowest point of its path?

9.  A 500 kg roller coaster is pulled to the top of a hill 45 m high and arrives at the top of the path with zero velocity.

a)  How much work is done the bringing the coaster to the top of the path?

b)  How fast will the car be going at the bottom of its path?

c)  How fast will the car be going at a point 29 m above the ground?

10.  State the impulse-momentum relationship. What is necessary to change the momentum of an object?

11.  A car of mass 1100 kg moves at 24 m/s. What is the momentum of the car?

12.  What braking force is necessary to stop the car in problem #12?

13.  Under what conditions is momentum conserved?

14.  Is momentum conserved in a) elastic collisions?

b) inelastic collisions?

15.  Is kinetic energy conserved in a) elastic collisions?

b) inelastic collisions?

16.  A 40 kg projectile leaves a 2000 kg launcher with a speed of 400 m/s. What is the recoil speed of the launcher?

17.  A 40 kg football player going through the air at 4 m/s tackles a 60 kg player who is heading towards her at 3 m/s, in the air. What is the speed and direction of the entangled players?

18.  A car of mass 1400 kg travels at 20 m/s and collides with a stationary truck of mass 2800 kg, with its parking brakes off. The two vehicles interlock as a result of the collision and slide along the icy road. What is the velocity of the car-truck system?

19. Calculate the value of v.

The two objects stick and move together. Calculate the speed after the collision.

20.


Heat and Thermodynamics
3. Energy cannot be created or destroyed, although in many processes energy is transferred to the environment as heat. As a basis for understanding this concept:

a. Students know heat flow and work are two forms of energy transfer between systems.

b. Students know that the work done by a heat engine that is working in a cycle is the difference between the heat flow into the engine at high temperature and the heat flow out at a lower temperature (first law of thermodynamics) and that this is an example of the law of conservation of energy.

c. Students know the internal energy of an object includes the energy of random motion of the object's atoms and molecules, often referred to as thermal energy. The greater the temperature of the object, the greater the energy of motion of the atoms and molecules that make up the object.

d. Students know that most processes tend to decrease the order of a system over time and that energy levels are eventually distributed uniformly.

e. Students know that entropy is a quantity that measures the order or disorder of a system and that this quantity is larger for a more disordered system.

Problems and Questions.

1.  What is the lowest possible temperature on the Celsius scale? On the Kelvin scale?

2.  What is the difference between heat and thermal energy?

3.  What are two ways of transferring energy between two objects?

4.  State the first law of thermodynamics. How does this relate to the law of conservation of energy?

5.  What is internal energy?

6.  What is thermal energy? How is this related to internal energy?

7.  Thermal energy depends on what quantity of the object?

8.  State two forms of the second law of thermodynamics. ( p. 360 and 365)

9.  Use the diagram on p.361 to explain the fist and second law.

10.  With respect to orderly and disorderly states, what do natural systems tend to do? Can a disorderly state ever transform to an orderly state?

11.  What is entropy?

12.  Which has more entropy- ice or liquid water at the same temperature? Liquid water or steam? Salt crystals or salt dissolved in water?

13.  Under what conditions can entropy decrease in a system?


Waves
4. Waves have characteristic properties that do not depend on the type of wave. As a basis for understanding this concept:

a. Students know waves carry energy from one place to another.
b. Students know how to identify transverse and longitudinal waves in mechanical media, such as springs and ropes, and on the earth (seismic waves).

c. Students know how to solve problems involving wavelength, frequency, and wave speed.

d. Students know sound is a longitudinal wave whose speed depends on the properties of the medium in which it propagates.

e. Students know radio waves, light, and X-rays are different wavelength bands in the spectrum of electromagnetic waves whose speed in a vacuum is approximately 3 x 108m/s (186,000 miles/second).

f. Students know how to identify the characteristic properties of waves: interference (beats), diffraction, refraction, Doppler effect, and polarization.

Problems and Questions.

1.  A ______transmits energy without transferring matter.

2.  What is the difference between a transverse wave and a longitudinal wave?

3.  Classify as transverse or longitudinal wave:

Waves on a string

Sound wave

Electromagnetic waves

Visible light

Compressions and stretches on a slinky

Radio waves

4.  The lowest frequency we can hear is about 20 Hz. Calculate the wavelength associated with this wave. The speed of the wave is 340 m/s.

5.  Calculate the speed of waves in a puddle that are 0.15 m apart and have a frequency of 2 Hz.

6.  Red light has a longer wavelength than violet light. Which has the greater frequency?

7.  Can light travel in a vacuum? Can sound travel in a vacuum?

8.  How does the speed of sound compare in air, water and steel?

9.  Put these in the order of increasing wavelength:

Red light, violet light, ultraviolet light, IR, radio waves, x-rays, microwaves.

10.  Order waves in #9 in order of increasing frequency.

11.  An ambulance has its sirens on while approaching a pedestrian. Compared to the stationary source,

a)  how does the speed of sound change?