Physics 1101 In-Class Problems: Kinematics

1. Initially, a ball has a speed of 5.0 m/s as it rolls up an incline. Some time later, at a distance of 5.5 m up the incline, the ball has a speed of 1.5 m/s DOWN the incline.
   (a) What is the acceleration? What is the average velocity? How much time did this take?
   (b) At some point the velocity of the ball had to have been zero. Where and when did this occur?

2. A bullet in a rifle accelerates uniformly from rest at a = 70000 m/s². If the velocity of the bullet as it leaves the muzzle is 500 m/s, how long is the rifle barrel? How long did it take for the bullet to travel the length of the barrel? What is the average velocity of the bullet?

3. A red car is stopped at a red light. As the light turns green, it accelerates forward at 2.00 m/s². At the exact same instant, a blue car passes by traveling at 62.0 km/h. When and how far down the road will the cars again meet? Sketch the d versus t motion for each car on the same graph. What was the average velocity of the red car for this time interval? For the blue car? Compare the two and explain the result?

4. A speeding motorist traveling down a straight highway at 110 km/h passes a parked patrol car. It takes the police constable 1.0 s to take a radar reading and to start up his car. The police vehicle accelerates from rest at 2.1 m/s². When the constable catches up with the speeder, how far down the road are they and how much time has elapsed since the two cars passed one another?

5. A ball is thrown up into the air with an initial velocity of 12.0 m/s. How long will it be in air until it returns to your hand? To what maximum height will it rise?

6. A ball is thrown up into the air and returns to the same level. It is in the air for 3.20 seconds. With what initial velocity was it thrown? How high did it rise?

7. Two balls are thrown upwards from the same spot 1.15 seconds apart. The first ball had an initial velocity of 15.0 m/s and the second was 12.0 m/s. At what height do they collide?

8. You are trapped on the top of a burning building. Death is imminent and help is nowhere in sight. There is a safe building 6.50 m away and 3.00 m lower. You decide to try and make it across. You run horizontally off your building at 8.10 m/s. Do you make it across? If you don't, how much faster must you be going?

9. A stunt motorcyclist is trying to jump over fifteen buses set side to side. Each bus is 2.50 m wide and a 30.0° ramp has been installed on either side of the line of buses. What is the minimum speed at which she must travel to safely reach the other side? How long will she be in the air?

10. A boy throws a rock with speed v = 18.3 m/s at an angle of θ = 57.0° over a building. The rock lands on the roof 22.0 m in the x direction from the boy. How long was the rock in the air? How much taller, height h, is the building than the boy? Ignore air resistance.

    

11. A tile, initially at rest, slides down a roof for a distance of 3.75 m before falling off the roof. The height of the building from ground to eave is 8.40 m. The acceleration of the tile as it slides is 2.10 m/s².
    (a) Determine the speed of the tile just as it leaves the roof.
    (b) Determine the vertical component of the velocity just before it leaves the roof.
    (c) Determine the horizontal component of the velocity just before it leaves the roof.
    (d) Determine how long it takes to hit the ground after leaving the roof.
    (e) Determine how far from the edge of the roof that the tile lands.

    

12. A boy is on the side of a hill. The hill makes a 15° incline with respect to horizontal. The boy throws a rock up the side of the hill. The boy throws the rock at 45° with respect to horizontal and the rock lands 30 m away up the hill. Find how fast the boy threw the rock. What angle does the rock make with horizontal before it lands? Ignore the boy’s height.

13. You are 6.0 m from the wall of a house. You want to toss a ball to your friend who is 6.0 m from the opposite wall. The throw and catch each occur 1.0 m above the ground.
    (a) What minimum velocity, expressed in ij notation, will allow the ball to clear the roof?
    (b) At what angle and speed do you throw the ball?

    

14. A boy throws a ball horizontally from a shoulder height of 1.10 m. Just before the ball touches down on the level ground it makes an angle of 30° with the ground. Determine the initial velocity of the ball as it left the boy’s hand.

15. The earth is 1.50 × 10¹¹ m from the sun. It takes 365 days for the earth to travel in a circle around the sun. What centripetal acceleration is felt by the earth?

Questions? mike.coombes@kpu.ca