Exams & Certification
A police officer is called in for accident reconstruction. He measures 11-meter long skid marks and he knows that for that particular tire/pavement combination, the coefficient of kinetic friction is 0.65. He also knows that the car was traveling at 3.5 m/s just before impact (the end of the skid marks). What was the speed […]
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A stone is dropped from the roof of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a speed of 12.0 m/s? The correct answer and explanation is : To determine the distance between two stones dropped from a building—one initially
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From the edge of a cliff, a gun fires a pellet straight upward. The pellet’s speed after leaving the gun is 30 m/s; the cliff is 75 meters tall. Assume that the ground is at height = 0 and that the positive direction is upward. At what time does the pellet hit the ground? The
From the edge of a cliff, a gun fires a pellet straight upward Read More »
A car starts from rest and accelerates at a constant 1.5 m/s2. Some time later, it takes 2.1 s to cross over a 25-meter long bridge. How far did the car travel before getting onto the bridge? The correct answer and explanation is : The car traveled 35.57 meters before getting onto the bridge. Explanation:
A car starts from rest and accelerates at a constant 1.5 m/s2 Read More »
You are driving in a car at 15 m/s, approaching an intersection that is 8.0 meters long. When you are 35 m away from the beginning of the intersection, the light turns yellow – it will turn red in 2.0 seconds. You must decide if you will hit the gas or the brakes. By hitting
You are driving in a car at 15 m/s, approaching an intersection that is 8.0 meters long Read More »
A skier covers the final 110 meters of a race in 5.0 seconds, crossing the finish line at a speed of 24 m/s. What was her (constant) acceleration? The correct answer and explanation is : The skier’s constant acceleration is 0.80 m/s². Explanation: We are given: To find the constant acceleration, we use kinematic equations.
A skier covers the final 110 meters of a race in 5.0 seconds Read More »
A window washer drops a bucket from his perch on a tall building. Through her window, an accountant in an office on a lower floor sees the bucket fall. It takes 0.30 s to fall past her window that is 2.2 m tall.How high is the window washer above the bottom of her window?What is
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An airplane flying horizontally with a speed of 500 km/h at a height of 950 m fires a projectile horizontally in its direction of motion at a speed of 265 m/s relative to the plane. (Calculate the following answers relative to the ground.)(a) How far in front of the release point does the projectile hit
A fast squirrel is running down a tree at a constant 4.0 m/s. It brushes an acorn with its tail and knocks it loose. The acorn falls and eventually hits the squirrel’s tail.How far does the acorn fall before hitting the squirrel if it starts from rest?If the acorn is knocked with an initial velocity
A fast squirrel is running down a tree at a constant 4.0 m/s Read More »
An object of mass 4.00 kg is held motionless at the top of a ramp that is inclined at an angle of 35 degrees relative to horizontal. The object is given a gentle shove giving it an initial velocity of 4.00 m/s down the ramp. Exactly 0.443 seconds after being released, the object is 2.00