Practice Questions – ISCI 2002

Chapter 6 – Heat and Energy

SpecificHeatProblems

1. A 4.6-kg aluminum pan is heated on the stove from 20 C to 110 C. How much heat had to be transferred to the aluminum? The specific heat capacity of aluminum is 900 J/kg x C

2. What would be the final temperature when 100-g of 25 C water is mixed with 75-g of 40 C water?

3. How much heat must be supplied to a 5.00-kg pan to raise its temperature from 20 C to 100 C if the pan is made of iron? The specific heat of iron is 450 J/kg x C.

GeneralQuestions

1. When air is rapidly compressed, why does its temperature increase?

2. After a car has been driven for some distance, why does the air pressure in the tires increase?

3. Why does adding the same amount of heat to two different objects not necessarily produce the same increase in temperature?

4. A metal ball is just able to pass through a metal ring. When the ball is heated it is unable to pass through the ring. See number 16 page 117. Explain why.

5. Why is it important to protect water pipes so that they don’t freeze?

6. In terms of physics, why do some people cook potatoes wrapped in aluminum foil?

Chapter 2 - Speed, velocity and acceleration

  1. Calculate the speed of an object that moves 8 meters in 20 seconds.
  2. An object has an initial velocity of 4 m/s. After a period of 20 seconds the velocity of the object increases to 12 m/s. Calculate the acceleration of the object.
  3. There are two opposing forces on a box. A person applies a 50 N force on a box attempting to push it to the right. The frictional force opposing the box (floor) is approximately 35 N. Draw a vector diagram showing the forces and direction of the forces. What is the summation of the forces?

4. A 30-N force and a 20-N force are opposing an object in movement. Determine the net force.

5. A horizontal force of 100-N is required to push a box across the floor at a constant velocity. Draw this and show that the net force is zero.

6. The oceans level is currently rising at about 1.5 mm per year. Show that at this rate the sea level will be 3 meters higher in 2000 years.

7. What is the weight of a 60-kg person on the surface of the Earth in pounds? (1 kg = 2.2 pounds) (gravity = 9.8 m/s2)

8. Determine the acceleration of a car that moves from rest to 15.0 m/s in 10.0 seconds.

9. Determine the average speed of a truck that makes a 285-mile trip in 5.0 hours?

10. Do #8 and # 9 (Exercises) on page 34

11. Suppose that a freely falling object were somehow equipped with a speedometer. By how much would its speed reading increase with each second of the fall?

12. For a freely falling object dropped from rest, what is its acceleration at the end of the fifth second of the fall? At the end of the tenth second?

Chapter 3 - Newton’sLaws

  1. Determine the acceleration of an object which has a mass of 50-kg that has a 175 N force applied to it.
  2. The driving forces (unbalanced forces) on an acceleration car is 3-kg. The mass of the car itself is 3 kg. Determine the acceleration of the cart.
  3. You push with a 40-N horizontal force on a 4-kg mass resting on a horizontal surface. The horizontal frictional force is 12-N. Determine the acceleration of this object.
  4. A 747 Jumbo Jet of mass 30,000 kg experiences a 30,000 N thrust for each of four engines during takeoff. Show that its acceleration is 4 m/s2.
  5. You are standing on a skateboard near a wall and you push on the wall with a force of 30 N. How hard does the wall push on you? Show that if you have a mass of 60-kg your acceleration while pushing will be 0.5 m/s2.
  6. A rocket becomes progressively easier to accelerate as it travels through space. Why is this so?
  7. A common saying “It’s not the fall that hurts you; it’s the sudden stop”. Translate this into Newton’s Laws of Motion.
  8. Do problems 30 and 31 on pages 55 and 56.
  9. An airplane flying northeast encounters wind resistance of 70 km/hr (Y-force) and another resistance force of 33 km/hr (X-force). Draw the vector components. Calculate the resultant force.

Chapter 4 - MomentumandImpulse

  1. A 14-kg object is travelling at a speed of 10 m/s. Determine its momentum.
  2. An object has a momentum of 80 kg x m/s. It has a mass of 25 kg. Determine its velocity.
  3. A 5-kg cart moving at 4 m/s collides with another 5-kg cart that is stationary. What will be the velocity of the second cart after the collision?
  4. Calculate the power expended when a 200-N object is lifted a vertical distance of 2-m in a 2 –second period.
  5. A 125-g object is moving at a speed of 10 m/s. How much kinetic energy does this object possess?
  6. When fixing a flat tire you apply a force of 75-N to a car jack. You move the handle of the jack 50-cm. The car which is being jacked up possesses a 7000-N force. With each downward push, how much does the car move up?
  7. A car with a mass of 1000-kg moves at 20 m/s. Show that the braking force is needed to bring the car to a halt in 10-s is 2000-N.
  8. If a Mack Truck and a Honda Civic have a head-on collision, which vehicle will experience the greater force of impact? The greater impulse? The greater change in momentum? The greater acceleration?

Chapter 5 –Gravity

1. Calculate the force of gravity between the Earth (6.4 x 1024 kg) and the sun (2.0 x 1030 kg). The average distance between them is 1.5 x 1011 m.

2. Find the change in the force of gravity between two planets when the masses of both planets are doubled but the distance between them stays the same.

3. Find the change in the force of gravity between two planets when the masses remain the same but the distance between them is increased ten-fold.

4. By what factor would your weight change if the Earth’s diameter were doubled and its mass were doubled?

Chapter 7 – Electricity and Magnetism

1. When combing your hair, you scuff electrons from your hair onto the comb. Is your hair then positively or negatively charged? How about the comb?

2. Why is a good conductor of electricity also a good conductor of heat?

3. Are automobile headlights wired in parallel or in series? What is your evidence?

4. A certain device in a 120-V circuit has a current rating of 20-A. Determine the resistance of this device.

5. What is the current drawn by a 1200-W hair dryer connected to a 120-V (10-A system).

6. A 120-V line to a socket is limited to 15-A by a safety fuse, will it operate a 1200-W hair dryer?

7. At 10,000 Ω, how much current will flow through your body if you touch the terminals of a 12-V battery?

8. Determine the resistance of a toaster that draws a current of 6.0-A when connected to a 120-V circuit?