1. The unit for force is defined as 1 Newton = 1 kg m/s2. What is the weight in
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Question
1. The unit for force is defined as 1 Newton = 1 kg m/s2. What is the weight in Newtons of a 65-gram object? Weight = mass * (gravitation acceleration).
2. An icicle falls 20.0 m from the roof of a building. If air resistance can be neglected, how fast would it be moving right before hitting the top of a package 1.5 meters tall?
3. A car goes on a straight highway at 65 miles per hour for 20 minutes, rested 38 minutes, and then 70 miles per hour for an hour. What is the average velocity?
4. A car was traveling at 25 mph (11.18 m/s) on a residential street. The driver started to brake 0.45 seconds after he saw a cat in the middle of the road 15 meters ahead. The car slowed down uniformly. What must be the minimum acceleration to save the cat?
5. Write the equation definition for average velocity (include units):
6. Write the equation definition for average acceleration (include units):
7. Write the equation for Newton’s 2nd Law (include units):
8. Directions: Provide a short (one or two sentence) definition or description. State Newton’s 3rd Law.
9. Explain the difference between weight and mass and provide the unit used to measure each.
10. Your car comes equipped with a speedometer, an odometer, and clock. This is all the necessary equipment to measure both instantaneous and average velocity. Explain how you measure each.
11. A student stands on a bathroom scale in an elevator. When does, the scale indicate each of the following? a. Reading greater than the student’s actual weight. b. Two situations where the reading equal to the student’s actual weight. c. A reading of zero.
12. A ball sits in the middle of a toy wagon. As you begin to pull the wagon, describe the direction of the ball motion. How does Newton’s 1st Law explain this?
13. A car goes from 8.94 m/s (20 MPH) to 31.29 m/s (70 MPH) in 7 seconds. a. Find the acceleration of the car. b. If at 31.29 m/s (70 MPH) the car hits a tree coming to an abrupt stop in 0.2 seconds, find the acceleration.
14. A rock is dropped in a pit and hits the bottom 4.5 seconds later. a. How deep is the pit? b. How fast is the rock going when it hits bottom?
15. To measure the acceleration of gravity a student drops a ball from height of 1.2 meters. If the ball is in the air for 0.51 seconds. Find the acceleration of gravity as measured in this experiment.
Explanation / Answer
1) Weight = 0.065*9.8=0.637 N
2)Height through which icicle has to fall = 20-1.5=18.5m
velocity at after falling by that height=sqrt(2*9.8*18.5)=19.04 m/s
3)Total distance travelled = 65*(20/60) + 70 = 91.67 miles
Total time taken = 20+38+60=118 minutes = 118/60=1.9667 hrs
Average velocity = 91.67/1.9667 = 46.6 mph
4)Distance travelled in reaction time = 0.45*11.18 = 5m
Distance to cat remaining = 15-5=10m/s
Car has to stop in 10 m
acceleration required = 11.182/(2*10) = -6.25m/s2
Therefore the car should be decelerated at 6.25m/s2
5)Average velocity = total displacement(in meters)/total time takenin seconds).Unit of velocity is m/s
6)Average acceleration = change in velocity(m/s)/total time taken(in seconds).Unit of acceleration is m/s2
7)Newton's second law states that force applied is equal to rate of change of momentum
9) gravitational force experienced by a body of mass m is called weight.
10)Instantaneous velocity is given by speedometer reading
Average velocity can be determined by using odometer reading(which gives total distance travelled) and clock that gives total time taken.
11)a)If elevator accelerates upwards
b)elevator moving upwards with constant velocity
elevator moving downwards with constant velocity
c)elevator free falling
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