PH. Ch. 2

A rock is thrown straight up with an inital velocity of 24.5 m/s. What max height will the rock reach before starting to fall downward? (g equal to 9.8 m/s^2)

30.6 m

Maria throws two stones from the top edge of a building with a speed of 20 m/s. She throws one straight down and the other straight up. The first one hits the street in a time t1. About how much later is it before the second stone hits?

4 s

A rock is thrown straight up with an inital velocity of 19.6 m/s. What time interval elapses between the rock's being thrown and its return to the original launch point? ( g equals 9.8 m/s^2)

4.00 s

A ball is thrown upwards at 19.6 m/s. For its complete trip ( up and back down to starting postition), its average speed is:

9.8 m/s

In the case of constant acceleration, the avg velocity equals the instantaneous velocity:

Half-way through the time interval

An object moves 20 m east in 30 s and then returns to its starting point taking an additional 50 s. If west is chosen as the positive direction, what is the sign associated with the average velosity of the object?

0 (no sign)

A cheetah can run at approximately 100 km/hr. if both animals are running at full speed, with the gazelle 70.0 m ahead, how long before the cheetah catches its prey?

12.6s

An automobile driver puts on the brakes and decelerates from 30.0 m/s to zero in 10 s. What distance does the car travel?

150 m

A bird, accelerating from rest at a constant rate, experiences a displacement of 28 m in 11 s. What is the final velocity after 11 s?

...

Human reaction time is usually about .2 s. If your lab partner holds a ruler between your finger and thumb and releases it without warning, how far can you expect the ruler to fall before you catch it? The nearest value is

...

John throws a rock down with speed 14 m/s fromt he top of a 30-m tower. If g= 9.8 m/s^2 and air resistance is negligible, what is the rock's speed just as it hits the ground?

...

A bird, accelerating from rest at a constant rate, experiences a displacement of 28 m in 11 s. What is its acceleration?

.46 m/s^2

An object moves 20 m east in 30 s and then returns to its starting point taking an additional 50 s. If west is chosen as the positive direction, what is the average speed of the object?

.50 m/s

At the top of a cliff 100m high. Raoul throws a rock upward with velocity 15.0 m/s. How much later should he drop a second rock from rest so both rocks arrive simultaneously at the bottom of the cliff?

1.78 s

A baseball is released at rest from the top of the Washington Monument. It hits the ground after falling for 6.0 s. What was the height from which the ball was dropped? (g= 9.8 m/s^2 and assume air resistance is negligible)

1.8 x 10^2 m

A vehicle designed to operate on a drag strip accelerates from zero to 30 m/s while undergoing a straight line path displacement of 45 m. What is the vehicle's acceleration if its value may be assumed to be constant?

10 m/s^2

A European sports car dealer claims that his product will accelerate at a constant rate from rest to a speed of 100km/hr in 8 s. What distance will the sports car travel during the 8 s acceleration period? ( hint: first convert speed to m/s)

111 m

Norma releases a bowling ball from rest; it rolls down a ramp with constant acceleration. After half a second it has traveled .75 m. How far has it traveled after 2 s.?

12 m

A 50-g ball traveling at 25.0 m/s is bounced off a brick wall and rebounds at 22.0 m/s. A high-speed camera records this event. if the ball is in contact witht he wall for 3.50 m/s, what is the magnitude of the avg acceleration of the ball during this time interval?

13 400 m/s^2

A rock, released form rest fromt he top of a tower, hits the groun after 1.5 s. What is the speed of the rock as it hits the ground? ( g=9,8 m/s^2 and air resistance is negligible)

15 m/s

A cheetah can maintain its max speed of 100 km/hr for 30.0 s. What min. distance must a gazelle running 80.0 km/hr be ahead of the cheetah to escape?

167 m

A ball is pushed with an initial velocity of 4.0 m/s. The ball rolls down a hill with a constant acceleration of 1.6 m/s^2. The ball reaches the bottom of the hill in 8.0 s. What is the ball's velocity at the bottom of the hill?

17 m/s

A European sports car dealer claims that his car will accelerate at a constant rate from rest to 100 km/hr in 8.00 s. What is the speed after the first 5.00 s of acceleration? (hint: first convert the speed to m/s)

17.4 m/s

the distance of the Earth from the sun is 93 000 000 miles. If there are 3.15 x 10^7 s in one year, find the speed of the Earth in its orbit about the sun.

18.6 miles/s

A Cessna aircraft has a lift-off speed of 120 km/hr. What min constant acceleration does this require if the aircraft is to be airborne after a take-off run of 240m?

2.31 m/s^2

A bird, accelerating from rest at a constant rate, experiences a displacement of 28 m in 11 s. what is the average velocity?

2.5 m/s

When a drag strip vehicle reaches a velocity of 60 m/s, it begins a negative acceleration by releasing a drap chute and applying its brakes. While reducing its velocity back to zero, its acceleration along a straight line path is a constant -7.5 m/s^2. What displacement does is undergo during this deceleration period?

240 m

Gwen releases a rock at rest from the top of a 40-m tower. If g= 9.8 m/s^2 and air resistance is negligible, what is the speed of the rock as it hits the ground?

28 m/s

A European sports car dealer claims that his car will accelerate at a constant rate from rest to 100 km/hr in 8.00 s. if so, what is the acceleration? (hint: first convert speed to m/s)

3.47 m/s^2

Mt. Everest is more than 8 000 m high. How fast would an object be moving if it could free fall to sea level after being released from an 8 000 m elevation? (ignore air resistanct)

396 m/s

a truck moves 70m east, then moves 120 m west, and finally moves east again a distance of 90 m. If east is chosen as the positive directions, what is the truck's resultant displacement?

40 m

Omar throws a rock down with speed 12 m/s from the top of a tower. The rock hits the ground after 2.0 s. What is the height of the tower? (air resistance is negligible)

44 m

A rock is thrown straight down with an initial velocity of 14.5 m/s from a cliff. What is the rock's displacement after 2.0 s? (take g equal to 9.8 m/s^2)

49 m

A basketball player can jump 1.6 m off the hardwood floor. With what upward velocity did he leave the floor?

5.6 m/s

A railroad train travels forward along a straight track at 80.0 m/s for 1 000 m and then travels 50.0 m/s for the next 1 000 m. What is the average velocity?

61.5 m/s

A cart is given an initial velocity of 5.0 m/s and experiences a constant acceleration of 2.0 m/s^2. What is the magnitude of the cart's displacement during the first 6.0 s of its motion?

66 m

A drag racer starts from rest and accelerates at 10 m/s^2 for the entire distance of 400 m (1/4 mile). What is the velocity of the race car at the end of the run?

89 m/s

Two objects of different mass are released simultaneously from the top of a 20 m tower and fall to the ground. If air resistance is negligible, which statement best applies?

Both objects hit the ground together

In one- dimensional motion where the direction is indicated by a plus or minus sign, the average velocity of an object has which of the following properties?

It can be positive, negative, or zero.

In one- dimensional motion, the average speed of an object that moves from oone place to another and then back to its original place has which of the following properties?

It is positive.

An object is dropped from a height. Once it is moving, which of the following statements is true, at least at one point?

Its velocity is never equal to its acceleration.

Jeff throws a ball straight up. For which situation is the instataneous 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 is experience zero velocity and non-zero acceleration at the same time?

at the top of its trajectory

On a position vs. time graph, the slope of the straight line joining 2 points on the plotted curve that are seperated in time by the interval Delta t, is which of the following quantities?

average velocity

A strobe photograph shows equally speed images of a car moving along a straight road. If the time intervals between images is constant, which of the following cannot be positive?

avg 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?

avg. acceleration of the car

A ball is thrown vertically upwards at 19.6 m/s. for its complete trip (up and back down to the starting position), its average velocity is:

not given. (bc the average velocity would be 0)

If the displacement of an object is given in SI units by delta x= -3t + 4t^2, at t= 2s, its vcelocity and acceleration are, respectively:

positive, positive

The value of an object's acceleration may be characterized in equivalent words by which of the following?

rate of change of velocity.

Changing the positive direction in a reference frame to the opposite direction does not change the sign of which of the following quantities?

speed; does change velocity, avg velocity, and displacement

Which is not a vector quantity

temperature

An x vs. t graph is drawn for a ball moving in one direction. The graph starts at the origin and at t=5 s the velocity of the ball is zero. We can be positive that at t=5 s,...

the ball has stopped

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.

displacement is which of the following types of quantities?

vector

A change in a physical quantity 'w' having initial value 'w initial' and final value 'w f' is given by which of the following?

wf - w initial