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# Tag: Time

#### A powerful motorcycle can accelerate from rest to 26.8 m/s (100 km/h) in only 3.90 s.

(a) What is its average acceleration?

(b) How far does it travel in that time? Continue reading “College Physics Problem 2.28”

#### In a slap shot, a hockey player accelerates the puck from a velocity of 8.00 m/s to 40.0 m/s in the same direction. If this shot takes , calculate the distance over which the puck accelerates. Continue reading “College Physics Problem 2.27”

#### Blood is accelerated from rest to 30.0 cm/s in a distance of 1.80 cm by the left ventricle of the heart.

(a) Make a sketch of the solution.

(b) List the knowns in this problem.

(c) How long does the acceleration take? To solve this part, first identify the unknown, and then discuss how you chose the appropriate equation to solve for it. After choosing the equation, show your steps in solving for the unknown, checking your units.

(d) Is the answer reasonable when compared with the time for a heartbeat?

#### At the end of a race, a runner decelerates from a velocity of 9.00 m/s at a rate of .

(a) How far does she travel in the next 5.00 s?

(b) What is her final velocity?

(c) Evaluate the result. Does it make sense?

#### An Olympic-class sprinter starts a race with an acceleration of .

(a) What is her speed 2.40 s later?

(b) Sketch a graph of her position vs. time for this period.

#### Assume that an intercontinental ballistic missile goes from rest to a suborbital speed of 6.50 km/s in 60.0 s (the actual speed and time are classified). What is its average acceleration in and in multiples of ?

#### A commuter backs her car out of her garage with an acceleration of .

(a) How long does it take her to reach a speed of 2.00 m/s?

(b) If she then brakes to a stop in 0.800 s, what is her deceleration?

#### Dr. John Paul Stapp was U.S. Air Force officer who studied the effects of extreme deceleration on the human body. On December 10, 1954, Stapp rode a rocket sled, accelerating from rest to a top speed of 282 m/s (1015 km/h) in 5.00 s, and was brought jarringly back to rest in only 1.40 s! Calculate his

(a) acceleration and

(b) deceleration.

Express each in multiples of by taking its ratio to the acceleration of gravity.

#### A cheetah can accelerate from rest to a speed of 30.0 m/s in 7.00 s. What is its acceleration?

#### The planetary model of the atom pictures electrons orbiting the atomic nucleus much as planets orbit the Sun. In this model, you can view hydrogen, the simplest atom, as having a single electron in a circular orbit in diameter.

(a) If the average speed of the electron in this orbit is known to be , calculate the number of revolutions per second it makes about the nucleus.

(b) What is the electron’s average velocity?

(a) What is its average acceleration?

(b) How far does it travel in that time? Continue reading “College Physics Problem 2.28”

(a) Make a sketch of the solution.

(b) List the knowns in this problem.

(c) How long does the acceleration take? To solve this part, first identify the unknown, and then discuss how you chose the appropriate equation to solve for it. After choosing the equation, show your steps in solving for the unknown, checking your units.

(d) Is the answer reasonable when compared with the time for a heartbeat?

(a) How far does she travel in the next 5.00 s?

(b) What is her final velocity?

(c) Evaluate the result. Does it make sense?

(a) What is her speed 2.40 s later?

(b) Sketch a graph of her position vs. time for this period.

(a) How long does it take her to reach a speed of 2.00 m/s?

(b) If she then brakes to a stop in 0.800 s, what is her deceleration?

(a) acceleration and

(b) deceleration.

Express each in multiples of by taking its ratio to the acceleration of gravity.

(a) If the average speed of the electron in this orbit is known to be , calculate the number of revolutions per second it makes about the nucleus.

(b) What is the electron’s average velocity?