Physics 80

joe can pitch a baseball a distance of 48 meters in 1.5 seconds. how fast is his pitch? a) 3.1 m/s b) 32 m/s c) 48 m/s d) 72 m/s

2) if c moves to position 5 (60 meters), what is its average velocity during these 5 seconds? a) 10 m/s b) 11 m/s c) 12 m/s d) 13 m/s

3) consider the motion diagram. it illustrates a car's velocity (v) and acceleration (a). the best description of a car’s velocity in this diagram is: a) a car’s velocity remained the same at 10 m/s. b) a car’s velocity decreased from 10 m/s to 5 m/s. c) a car increased its velocity from 5 m/s to 10 m/s. d) a car increased its velocity from -5 m/s to -1 m/s.

4) displacement is to velocity as is to acceleration. a) direction b) speed c) time d) velocity

5) ridge x moves a total of 25 cm in 5 years. what is its rate of movement, expressed in cm/year? a) 1/5 cm/year b) 5/25 cm/year c) 5/1 cm/year d) 1/25 cm/year

6) consider these four line graphs representing speed in meters/second, where each x-axis is labeled in seconds and each y-axis is labelled in meters. which graph represents an average speed of 1.57 m/s * hover over answer image to enlarge

7) a car's position in relation to time is plotted on the graph. what can be said about the car during segment b? a) the car travels for 80 seconds during segment b. b) the car has come to a stop and has zero velocity. c) the car is traveling faster during segment b than in segment c. d) the car is traveling with a constant velocity due to the flat line of the graph.

8) diego kicks a soccer ball from the end line. his fellow students time and mark the soccer ball as it moves down the field. the graph represents the ball's progress. based on the graph, during what time is the soccer ball not moving? a) from 0 to 1.5 seconds b) from 3.0 to 4.5 seconds c) from 4.5 to 5.0 seconds d) from 1.5 to 3.0 seconds

9) speed graph time (s) distance (m) 0 0 1 3 2 6 3 12 4 16 consider the data table charting the speed of a toy car moving across the floor. the line graph representing this data would best be described as a a) curved line with varying slope. b) diagonal line with a slope of 3. c) horizontal line with a slope of 3. d) diagonal line with varying slope, from 3 to 4.

10) a rock is whirled around in a circle with a slingshot. as the rock leaves the slingshot, it has an instantaneous velocity in a straight line. how do newton's laws of motion explain this? a) gravity does not exert a force on the rock until it leaves the slingshot. b) once the slingshot is not exerting a force on the rock it will slow down and stop. c) air resistance keeps the rock from moving in a circle after it leaves the slingshot. d) to move in a circle requires an acceleration and therefore a net force. this force is supplied by the slingshot.

11) using newton's law of gravity: f = gm1m2/d2 and fnet = ma, we can calculate the acceleration of a satellite. what will happen to the acceleration of a satellite if the mass and the distance from the center of the earth is doubled? a) the acceleration will not change. b) the acceleration will become 1/4 as much. c) the acceleration will become 1/2 as much. d) the acceleration will become twice as much.

12) the velocity of an object is equal to the distance divided by time. the equation is velocity = distance/time. if you wanted to calculate the time required for an object to travel a distance and you knew the velocity, you would a) multiply: velocity x distance. b) subtract: velocity – distance. c) divide: distance ÷ velocity d) add: velocity + distance

13) a kite is traveling in the sky at a velocity of 5 km h . if you are walking underneath the kite in the opposite direction at a rate of 3 km h , what is the kite's velocity relative to you on the ground? a) -8 km h b) -2 km h c) 5 km h d) 8 km h

1.  B) 32 m/s

The speed of the baseball is given by

where

d = 48 m is the distance travelled

t = 1.5 s is the time taken

Substituting,

2. C) 12 m/s

The average velocity is given by

where

d = 60 - 0 = 60 m is the displacement

t = 5 s is the time interval

Substituting,

3. Missing diagram

4. D) velocity

In fact, velocity is defined as the ratio between the displacement () and the time interval () needed to achieve that change in position:

Similarly, acceleration is defined as the ratio between the change in velocity () and the time interval ():

Comparing the two equations, we see that displacement is to velocity as velocity is to acceleration.

5. C) 5/1 cm/year

We know that the ridge moves 25 cm in 5 years, so we have:

- Displacement (d): d = 25 cm

- Time interval (t): t = 5 y

Using the equation for the velocity:

6.  D

The missing graph is attached. Each graph represents a distance (on the y-axis, measured in metres) versus a time (on the x-axis, measured in seconds). Therefore, the speed in each graph can be simply calculated from the slope of the curve, since speed is the ratio between distance and time:

For each graph:

A.

B.

C.

D.

So we can say that the correct graph must be graph D, the closest to 1.57.

7. B) The car has come to a stop and has zero velocity

The missing graph is attached.

The graph shows the position of the car versus time. From the graph, we can see that in segment B, the position of the car does not change: this means that its velocity is zero, since the velocity is defined as the ratio between the change in position (displacement) and the time interval:

And since the displacement is zero, the velocity is also zero.

8.  C) from 4.5 to 5.0 seconds

Missing graph is attached.

The graph represents the distance covered versus the time taken: therefore, the speed of the ball can be evaluated from the slope of the curve.

The only region in which the slope of the curve is zero is between 4.5 seconds and 5.0 seconds: therefore, this is the region where the soccer ball is not moving.

9. D) diagonal line with varying slope, from 3 to 4.

The table of data is:

Time (s)  0 1 2 3 4

Distance (m) 0 3 6 12 16

We want to know how the distance/time graph would like like. We have:

- At t = 1, the distance is , so the slope is

- Similarly, at t = 2:  

- Instead, at t =3, the slope is

- Similarly, at t=4,

So the correct answer is D.

10. D) To move in a circle requires an acceleration and therefore a net force. This force is supplied by the slingshot.

For an object in circular motion, the velocity constantly changes (because the direction changes): this means that an acceleration is required (towards the centre of the circle), and therefore a force must be exerted (also towards the centre of the circle) to keep the object in the circular path.

As soon as this force is removed, the object is "free" to leave the circular trajectory and continue its motion following a straight path at constant velocity, according to Newton's first law.

11. B) The acceleration will become 1/4 as much.

Re-arranging Newton's second law formula,

(1)

The force exerted on the satellite is actually the force of gravity:

(2)

Substituting (2) into (1),

We see that there is no dependance on the mass of the satellite (m), but only on the distance. Since in this problem the distance is doubled (d'=2d), the new acceleration will be:

12. C) divide: distance : velocity

Velocity is distance divided by time:

Multiplying by t on both sides,

and dividing by v on both sides,

13. A) -8 km/h

Let's call:

the velocity of the kite

your velocity (opposite direction)

In your frame of reference, the velocity of the kite will be:

show the wavelengths of a wave. show the crests of a wave.

the temperature and the pressure affect solubility. temperature affects by changing the properties of the solvent. the increase in pressure increases solubility, the decrease in pressure decreases solubility.