110 likes | 265 Views
Speed, Velocity, Acceleration. Chapter 39. Speed. The speed of an object is the distance it travels in unit time( units : m/s ). Speed = Distance Time. Different speeds. Below are some examples of different speeds: Speed of a common snail = 0.0036 km/h (0.0023 mph)
E N D
Speed, Velocity, Acceleration Chapter 39
Speed • The speed of an object is the distance it travels in unit time(units : m/s). Speed = Distance Time
Different speeds • Below are some examples of different speeds: • Speed of a common snail = 0.0036 km/h (0.0023 mph) • A brisk walk = 6km/h (3.75 mph) • Olympic sprinters = 36km/h (22.5 mph) (average speed over 100 metres) • Speed limit on a Frenchautoroute = 130km/h (80 mph) • Top cruising speed of a Boeing 747-400 = 913km/h (567 mph) • Official air speed record = 3,529 km/h (2,188 mph) • Space shuttle on re-entry = 28,000km/h (17,500 mph
Velocity • Velocity is speed in a given direction. i.e. 10m/s due south.
Acceleration. • Acceleration is the change in velocity per second.(Units m/s2) The velocity of a car changes from 9m/s to 27m/s in 6 s.What is its acceleration? Answer: Acceleration = Final velocity – Initial velocity Time taken = 27m/s - 9m/s 6s = 3m/s/s.
Draw a graph of the following table i. Which walker is going faster? ii. How long does it take for walker B to travel 11 m? iii. How far apart are the walkers after 2.5 sec? iv. Is the speed of walker A constant? v. What is the speed of each walker?
Answers. (i) Walker A (ii) 5.5 sec (iii) 2.5 m (iv) The graph for walker A is a straight line. Therefore A’s speed is a constant. (v)Walker A Speed = Distance21 = 3 m/s Time 7 Walker B Speed = Distance12 = 2m/s Time 6