Physics Topic 2
A ball is rolled horizontally off a table with an initial speed of 0.24 m/s. A stopwatch measures the ball's trajectory time from table to the floor to be 0.36 s. What is the height of the table? (g = 9.8 m/s2 and air resistance is negligible)
(not 0.55m) think 0.64 m
A European sports car dealer claims that his product will accelerate at a constant rate from rest to a speed of 100 km/h in 6.00 s. What distance will the sports car travel during the 6.00-s acceleration period? (Hint: First convert speed to m/s.)
(not 41.7)
A car is moving along a straight highway and accelerates at a constant rate while going from point A to point B. If the acceleration is positive, increasing the speed of the car, where does the position where the instantaneous speed equals the average speed occur for the interval from A to B?
(not any of the answers could be correct)
A ball of relatively low density is thrown upwards. Because of air resistance the acceleration while traveling upwards is −10.8 m/s2. On its trip downward the resistance is in the opposite direction, and the resulting acceleration is −8.8 m/s2. When the ball reaches the level from which it was thrown, how does its speed compare to that with which it was thrown?
(not it is greater than the original speed upward)
A track star in the broad jump goes into the jump at 12.0 m/s and launches himself at 26.0° above the horizontal. How long is he in the air before returning to Earth? (g = 9.8 m/s2)
1.1 s
A 50.0-g ball traveling at 22.0 m/s is bounced off a brick wall and rebounds at 21.0 m/s. A high-speed camera records this event. If the ball is in contact with the wall for 2.50 ms, what is the average acceleration of the ball during this time interval?
1.72E+4 m/s2
In which of the following cases is the displacement's magnitude half the distance traveled?
12 steps east followed by 4 steps west
A ball is thrown vertically upwards at 24.5 m/s. For its complete trip (up and back down to the starting position), its average speed is
12.3 m/s
A startled deer runs 520 m at 20.0° north of east for half a minute, then turns and runs 380 m at 55.0° north of west for 15.0 seconds and stops. What is the average velocity of the deer during this time?
12.4 m/s
A bridge that was 10.4 m long has been washed out by the rain several days ago. How fast must a car be going to successfully jump the stream, if we neglect air resistance? Although the road is level on both sides of the bridge, the road on the far side is 3.00 m lower than the road on this side.
13.3 m/s
A European sports car dealer claims that his product will accelerate at a constant rate from rest to a speed of 100 km/hr in 8.00 s. What is the speed after the first 4.00 s of acceleration? (Hint: First convert the speed to m/s.)
13.9
John throws a baseball from the outfield from shoulder height, at an initial velocity of 41.5 m/s at an initial angle of 40.0° with respect to the horizontal. The ball is in its trajectory for a total interval of 5.00 s before the third baseman catches it at an equal shoulder-height level. (Assume air resistance negligible.) What is the ball's horizontal displacement?
159 m
A car's initial velocity is 50.0 km/h in the direction 60.0° north of east, and its final velocity is 70.0 km/h in the direction 40.0° south of east. If the time period for this journey is 30.0 minutes, what is the magnitude of the car's average acceleration?
186 km/h
A Cessna aircraft has a lift-off speed of 135 km/h. What minimum constant acceleration does this require if the aircraft is to be airborne after a take-off run of 260 m?
2.70 m/s
A plane is moving due north, directly towards its destination. Its airspeed is 210 mph. A constant breeze is blowing from west to east at 20.0 mph. At what rate is the plane moving north?
209 mph
A boat moves at 10.8 m/s relative to the water. If the boat is in a river where the current is 2.00 m/s, how long does it take the boat to make a complete round trip of 1 100 m upstream followed by a 1 100-m trip downstream?
211 s
A stone is thrown with an initial speed of 11.5 m/s at an angle of 50.0 above the horizontal from the top of a 30.0-m-tall building. Assume air resistance is negligible, and g = 9.8 m/s2. What is the magnitude of the horizontal displacement of the rock?
26.1 m
A fireman, 57.6 m away from a burning building, directs a stream of water from a fire hose at an angle of 35.2° above the horizontal. If the initial speed of the stream is 42.7 m/s, at what height will the stream of water strike the building?
27.3 m
Gwen releases a rock at rest from the top of a 40-m tower. If g = 9.8 m/s2 and air resistance is negligible, what is the speed of the rock as it hits the ground?
28 m/s
An object, initially moving in the negative x-direction, is subjected to a change in velocity in the positive y-direction. If the resulting velocity vector is drawn from the origin, into which quadrant does this vector point? 1st
2nd
Amanda is standing at the edge of a cliff. She throws a rock vertically upward at speed v0, while at the same time throws a second rock vertically downward at the same speed. How long after the rock thrown downward hits the ground does the rock thrown upwards hit?
2v0/g
Omar throws a rock down with speed 12.5 m/s from the top of a tower. The rock hits the ground after 1.50 s. What is the height of the tower? (air resistance is negligible)
30.0 m
A rock is thrown straight up with an initial velocity of 25.0 m/s. What maximum height will the rock reach before starting to fall downward? (Take acceleration due to gravity as 9.80 m/s2.)
31.9 m
Plane A is flying at 440 mph in the northeast direction relative to the Earth. Plane B is flying at 550 mph in the north direction relative to the Earth. What is the speed of Plane B as observed from Plane A?
392 mph
A boat travels upstream and after one hour has gone 10 km. The boat next travels downstream and after one hour has gone 18 km. If the boat's speed relative to the water is constant, what is the speed of the current in the river?
4 km/h
A ball is launched from ground level at 25 m/s at an angle of 31° above the horizontal. How far does it go before it is at ground level again?
56 m
A jet airliner moving at 470 mph due east moves into a region where the wind is blowing at 110 mph in a direction 30.0° north of east. What is the new velocity and direction of the aircraft?
568 mph, 5.56° N of E
A plane is moving due north, directly towards its destination. Its airspeed is 210 mph. A constant breeze is blowing from west to east at 25.0 mph. In which direction is the plane pointed?
6.79° W of N
A stone is thrown with an initial speed of 11.5 m/s at an angle of 50.0 above the horizontal from the top of a 30.0-m-tall building. Assume air resistance is negligible, and g = 9.8 m/s2. What is the magnitude of the horizontal-velocity component of the rock as it hits the ground?
7.39 m/s
A cheetah can maintain its maximum speed of 96.0 km/hr for 26.0 seconds. What minimum distance must a gazelle running 85.0 km/hr be ahead of the cheetah to escape?
79 m
A rifle is aimed horizontally toward the center of a target 120 m away. If the bullet strikes 11.2 cm below the center, what was the velocity of the bullet? (Ignore air friction.)
790 m/s
A stone is thrown at an angle of 30° above the horizontal from the top edge of a cliff with an initial speed of 12 m/s. A stop watch measures the stone's trajectory time from top of cliff to bottom to be 4.8 s. What is the height of the cliff? (g = 9.8 m/s2 and air resistance is negligible)
84 m
A cheetah can run at approximately 100 km/h and a gazelle at 80.0 km/h. If both animals are running at full speed, with the gazelle 50.0 m ahead, how long before the cheetah catches its prey?
9.0 s
A projectile is fired at an angle of elevation of 30°. Neglecting air resistance, what are possible angles in flight between the acceleration vector and the velocity vector?
90 and 30
Starting from rest, a car accelerates down a straight road with constant acceleration a for a time t, then the direction of the acceleration is reversed, (i.e., it is −a), and the car comes to a stop in an additional time t, the time for the whole trip being 2t. At what time, or times, is the average velocity of the car for the trip equal to its instantaneous velocity during the trip?
This occurs at 2 times, 0.5t and 1.5t.
Consider the magnitude of the average speed, vavg, speed, mag, and the magnitude of the average velocity, vavg, velocity, mag, for the same trip. Which of the following is always true?
Vavg, speed, mag > Vavg, velocity, mag
Which formula is dimensionally consistent with an expression yielding a value for velocity? (a is acceleration, x is distance, and t is time)
at
Jeff throws a ball straight up. For which situation is the vertical velocity zero?
at the top
A baseball catcher throws a ball vertically upward and catches it in the same spot when it returns to his mitt. At what point in the ball's path does it experience zero velocity and non-zero acceleration at the same time?
at the top of its trajectory
In a two-dimensional Cartesian coordinate system the x-component of a given vector is equal to that vector's magnitude multiplied by which trigonometric function, with respect to the angle between vector and x-axis?
cosine
In a two-dimensional Cartesian system, the x-component of a vector is known, and the angle between vector and x-axis is known. Which operation is used to calculate the magnitude of the vector? (taken with respect to the x-component)
dividing by cosine
In the case of constant acceleration, the average velocity equals the instantaneous velocity:
half-way through the time interval.
A plane is moving due north, directly towards its destination. Its airspeed is 220 mph. A constant breeze is blowing from west to east at 50 mph. How long will it take for the plane to travel 220 miles north?
more than one hour
A hiker walks 200 m west and then walks 100 m north. In what direction is her resulting displacement?
none of the answers are correct (not northwest)
A strobe photograph shows equally-spaced images of a car moving along a straight road. If the time intervals between images is constant, which of the following cannot be positive?
the acceleration of the car
A strobe photograph of a car moving along a straight road shows the interval between each successive image to be diminishing. If the direction of motion of the car is taken as positive, which of the following is/are negative?
the average accleration of the car
On a velocity-time graph for a particle, suppose the plot starts at some positive velocity and then follows a straight line to zero at a later time. Which of the following must be true about a position vs. time graph for this same time interval?
the curve will rise steeply at first and as time goeson will level out approaching its highest position value at the later time
A projectile is launched at an angle θ above the horizontal. Three seconds later the projectile is moving the same angle θ below the horizontal. Which of the following (actual values with units, not just algebraic symbols) can be found from the information given?
the initial vertical componenet of the projectile's velocity
The slope of the acceleration vs. time curve represents
the rate of change of acceleration
A v vs. t graph is drawn for a ball moving in one direction. The graph starts at the origin and at t = 5 s the acceleration of the ball is zero. We know that at t = 5 s,
the velocity of the ball is not changing
