PHYSICS 1020

SOLUTION TO SECOND EXAM
3 February 1997

(Correct solution is indicated by ``(*)'')

  1. Whenever a force acts on a body, the body's speed must change.

    (a) True (b)(*) False

  2. If there were no air resistance, heavy objects would fall faster than light ones.

    (a) True (b)(*) False

  3. Since they have a much longer distance to cover, planets that are farther from the sun move on the average much faster in their orbits than the planets which are closer to the Sun.

    (a) True (b)(*) False

  4. The larger the mass of an object is, the smaller is its acceleration due to the action of a force.

    (a)(*) True (b) False

  5. On the surface of Jupiter, your mass would be about 3 times as large as what it is on Earth.

    (a) True (b)(*) False

  6. Two numbers are necessary to specify the position of a point on the surface of a sphere.

    (a)(*) True (b) False

  7. There is no stronger force than the force of gravity.

    (a) True (b)(*) False

  8. At the bottom of a very deep cave, your weight is bigger than at the surface.

    (a)(*) True (b) False

  9. According to Newton's law of action/reaction, when there is a force acting on an object, there is always an equally strong force in the opposite direction acting on the same object.

    (a) True (b)(*) False

  10. It is the equality of inertial and gravitational mass which is responsible for the fact that all bodies fall with the same acceleration.

    (a)(*) True (b) False

  11. A book lying on a table top is given a brief shove; it slides a short distance and then comes to rest. According to Aristotelian physics, it stopped because
    1. its inertia represents a resistance to motion and makes it stop.
    2. gravity pulls it down, so it cannot move horizontally.
    3. frictional forces slow it down until it stops.
    4. (*) being at rest is its natural state.
    5. the ether slowed it down.

  12. A book lying on a table top is given a brief shove; it slides a short distance and then comes to rest. According to Galilean/Newtonian physics, it stopped because
    1. its inertia represents a resistance to motion and makes it stop.
    2. gravity pulls it down, so it cannot move horizontally.
    3. (*) frictional forces slow it down until it stops.
    4. being at rest is its natural state.
    5. the ether slowed it down.

  13. If you throw a ball straight up, it will eventually come back down. The reason for this is the following:
    1. (*) the gravitational force causes the ball to accelerate downward, towards the center of the earth.
    2. balls like to be on the ground rather than in the air.
    3. air resistance - if there were no air, the ball would continue flying upward forever.
    4. it is really the earth which moves upward, but since we move with the earth, we perceive the ball to fall.
    5. it is the ball's inertia which prevents it from perpetual movement.

  14. When you push a table across the floor, according to Newton's law of action and reaction, the force exerted by the table on you is opposite to the force exerted by you on the table. Why is it that these two forces do not balance, and you actually can move the table (provided you are strong enough)?
    1. (*) Only one of these two forces acts on the table.
    2. The force by you on the table is larger than the force by the table on you.
    3. The floor pushes forward on the table.
    4. Newton's laws do not apply to tables.
    5. The frictional force exerted by the floor on you adds an additional push on the table.

  15. A satellite moves at a steady 20 000 km/hr in a circular orbit around Earth.
    1. It is in uniform motion because up there no force is acting on it, and therefore its speed does not change.
    2. Its speed is changing all the time, so it is in accelerated motion.
    3. Since its speed does not change, it is not accelerated, and therefore no force can be acting on it.
    4. It moves in a circular orbit because all objects in outer space move in circles.
    5. (*) Since the direction of its velocity changes, it is accelerated.

  16. You ride your bicycle 5 km to your physics class in 10 minutes; your average speed is
    1. 5 km/hr
    2. 10 km/hr
    3. 20 km/hr
    4. (*) 30 km/hr
    5. 40 km/hr

  17. A Martian picks up a rock and drops it into a big hole. The rock falls 8 Martian ``cubits'' in the first Martian ``tailwag'' of its fall. How many Martian cubits does the rock fall in four Martian tailwags? (Neglect the effect of Martian air resistance)
    1. 16 cubits
    2. 32 cubits
    3. 64 cubits
    4. (*) 128 cubits
    5. 256 cubits
    (A Martian cubit is the official Martian distance unit; it is a bit longer than a foot. A Martian tailwag is the official Martian time unit; it is a bit shorter than a second.)

  18. At the end of the first tailwag, the stone mentioned in the previous question has a speed of 16 cubits/tailwag. What is its speed after four tailwags? (Neglect the effect of Martian air resistance)
    1. 16 cubits/tailwag
    2. 32 cubits/tailwag
    3. (*) 64 cubits/tailwag
    4. 128 cubits/tailwag
    5. 256 cubits/tailwag

  19. While a marble is rolling down an inclined plane (frictionless), it is in motion with
    1. decreasing speed;
    2. decreasing acceleration;
    3. constant velocity;
    4. constant speed;
    5. (*) constant acceleration;

  20. An apple of weight 2 N is freely falling. Earth's mass is tex2html_wrap_inline166 kg. How strong is the force exerted by Earth on the apple?
    1. Since the apple is falling freely, there is no force acting on it.
    2. (*) The force is = 2 N.
    3. The force is = tex2html_wrap_inline168 N.
    4. The force depends on how high up the apple was when it started falling.
    5. The force varies, depending on how fast the ball is falling.

  21. If you weighed 800 newtons on Earth, how much would you weigh at about 6380 km (i.e. one Earth radius) above the Earth's surface (i.e. two Earth radii from Earth's center)?
    1. 100 newtons
    2. (*) 200 newtons
    3. 400 newtons
    4. 800 newtons
    5. 1600 newtons

  22. Suppose we could double the moon's mass, and at the same time double the distance between Earth and Moon. How would this affect the force that keeps the moon in orbit around Earth? The force would
    1. (*) be halved;
    2. be doubled;
    3. be quadrupled;
    4. be eight times as strong;
    5. remain unchanged;

  23. As the moon moves in its orbit around Earth, the net force on it is
    1. zero;
    2. directed outward, away from Earth;
    3. forward, along its direction of motion;
    4. backward, opposite to its direction of motion;
    5. (*) directed inward, toward Earth;

  24. Which of the following physics quantities is not a vector quantity:
    1. acceleration
    2. angular momentum
    3. (*) density
    4. momentum
    5. velocity

  25. A Ferrari racing car goes from 0 to 60 miles per hour in 3 seconds. What is its average acceleration during those 3 seconds?
    1. 3.6 tex2html_wrap_inline170
    2. 22.2 tex2html_wrap_inline172
    3. (*) 8.9 tex2html_wrap_inline174
    4. 36.2 tex2html_wrap_inline176
    5. 89.4 tex2html_wrap_inline178

  26. A book of mass 2.0 kg lies on your desk. What is the force (in newtons) exerted by the desk on the book?
    1. 0 N
    2. 2.0 N
    3. 9.8 N
    4. (*) 19.6 N
    5. 29.4 N

  27. A book of mass 2.0 kg lies on your desk. What is the net force (in newtons) exerted on the book?
    1. (*) 0 N
    2. 2.0 N
    3. 9.8 N
    4. 19.6 N
    5. 29.4 N

  28. Which of the following statements is false:
    1. A body in uniform motion has no acceleration.
    2. (*) When a body moves, a force must be acting on it.
    3. In circular motion with constant speed, the acceleration is perpendicular to the velocity.
    4. Near the surface of the Earth, free fall is motion with constant acceleration.
    5. When an object is in free fall, it is being accelerated.

  29. A car weighing 6000 N is travelling along a straight level road, powered by a drive force of 700 N. The force of air resistance is 250 N, and rolling resistance is 150 N. The net force on the car is
    1. 0 N
    2. 200 N forward
    3. (*) 300 N forward
    4. 700 N forward
    5. 6000 N downward

  30. Which of the following is the driving force on the car mentioned in the previous question?
    1. the forward push by the engine on the car;
    2. the backward push by the drive tires on the road;
    3. the perpendicular contact force by the road on the tires;
    4. the combined force due to gravitation and friction;
    5. (*) the forward push by the road on the tires;

  31. If the force of gravity suddenly were ``switched off'', the Moon would
    1. fly radially outward away from the earth.
    2. fall radially inward, onto the earth.
    3. continue orbiting the earth, but on a slightly larger orbit.
    4. stop in its orbit around the earth, and remain motionless forever.
    5. (*) move straight ahead, in the direction in which it was going when the gravitational force stopped.

  32. What force balances the force of gravity on a satellite when it is in orbit around Earth (thus keeping the satellite from falling down to Earth)?
    1. a balancing force is not needed because gravity does not act in outer space;
    2. (*) there is no balancing force - gravity is the only force acting on it;
    3. the attraction of the Moon;
    4. the centrifugal force;
    5. the force exerted by the Sun on the satellite;

  33. One newton is equal to
    1. tex2html_wrap_inline180
    2. tex2html_wrap_inline182
    3. tex2html_wrap_inline184
    4. (*) tex2html_wrap_inline186
    5. tex2html_wrap_inline188

  34. Which of these could not be used as a unit of acceleration?
    1. 1 (mile/hr)/second
    2. (*) 1 m/sec
    3. 1 (km/hr)/minute
    4. 1 tex2html_wrap_inline190
    5. 1 tex2html_wrap_inline192


home page for phy1020
Mon Feb 3 19:41:06 EST 1997