Speed and Velocity
What is the difference between a scalar quantity and a vector quantity?
Scalar= Magnitude only
Vector= Magnitude + Direction
Determine what the slopes of the following graphs represent:1.Distance-Time, 2.Displacement-Time, 3.Velocity-Time, 4.Speed-Time.
1. Average speed
2. Average velocity
3. Acceleration
4. Change in speed
What two things must occur for work to be done?
A force must act on the object and the object must move in the direction of the force.
A 123 baseball moves at 4.4 m/s. What is it's kinetic energy?
1.2 J
What does the law of conservation of energy state?
Energy cannot be created or destroyed. It can only be transferred or transformed.
A student walks 15.0m north in 5.0s, then 10m south in 5.0s.
What is the students average speed?
2.5 m/s
A car speeds up from 2.0 m/s [E] to 12.0 m/s [E] in 5.0s. What is the acceleration?
2.0 m/s2 [E]
4 x 101 J
A robin has a mass of 22 g and is sitting on a branch. Its gravitational potential energy relative to the ground is 1.72 J.
Calculate the height of the branch above the ground.
h= 8.0 m
A backpack falls off a desk with a speed of 0.30 m/s. Calculate the height of the backpack at this time.
A student walks 15.0m north in 5.0s, then 10m south in 5.0s.
What is the students average velocity?
0.50 m/s [N]
A cyclist accelerates at 3.0 m/s² for 6.0 s starting from rest.
What is their final velocity?
18 m/s
d= 8.7 m
A 20 kg object has 1960.55 J of gravitational potential energy. What height is it at?
h=10 m
A 80 kg skateboarder is moving at 10m/s and is 5.0m above the ground. What is their total mechanical energy?
7.9 x 103 J
A turtle travels 8.3 m north then turns and travels 4.52 m east.
a) What distance did the turtle travel?
b) What was the total displacement?
a) 13m
b) 9.5m [NE]
A skateboard slows down from 5.0 km/h [W] to 3.0 km/h [W] in 4.0 seconds. What is its acceleration?
0.14 m/s2[E]
A person stands still holding a suitcase. Is work being done?
No
Two objects have the same mass. One moves five times as fast as the other. Which has more kinetic energy and by how much?
The faster object has 25 times the kinetic energy.
A machine has 92% efficiency. It's output energy was 437 J. Calculate the input energy.
4.8 x 102 J
A cyclist travels
- 40m east in 8.0 s, 20m west in 4.0 seconds and 10m east in 2.0 seconds.
Find
a) total distance
b) total displacement
c) average velocity
a) 70m
b)30m[E]
c) 2.1m/s[E]
A car starts at 2.0 m/s and accelerates at 2.5m/s2 for 4.0 s. Find
1. Final velocity
2. Change in velocity
2. 10 m/s
A student pushes a 12.0 kg box across the floor with a force of 45 N for 8.0 m. During the motion, 120 J of energy is lost to friction. Calculate
1. Total work done by student
2. Useful work done on the box (hint:120 J of energy is lost to friction)
3. The efficiency of the system
1. 3.6 x 102 J
2. 2.4 x 102 J
3. 67%
A skateboarder starts at the top of a ramp with 7500 J of potential energy. At the bottom, their speed is 10.52 m/s. What is their mass? (Hint: What happens to potential energy at the bottom of a hill)
m= 135.5 kg
A skier starts with 10,345 J of gravitational potential energy. At the bottom, they have 7001.33 J on kinetic energy.
Find:
1. Energy Lost
2. Efficiency
1. 3343.7 J of energy lost
2. 67.678 %