2 physics problems involving speed?

J

Jill Z

New member
A car traveling 88 km/h is 130 m behind a truck traveling 75 km/h. How long will it take the car to reach the truck?

A bowling ball traveling with constant speed hits the pins at the end of a bowling lane 16.0 m long. The bowler hears the sound of the ball hitting the pins 2.90 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s. Answer to the nearest 0.001 m/s.

i don't get what formula to use and where i'm going wrong =/
 
Thje relative speed between the car and the truck is 13 km/h. At 13 km/h how long will it take to cover 130 m? (you better get .01 hours or 36 seconds).

Now... You go figure out the other one. All it takes is a little bit of 'horse sense'.

Doug
 
lets take the differences of the first

the car is catching up at (88-75) 13 km/h
it has to travel 130 m
13/ 3.6 = 3.611111 m/s
t = d/s
t= 130/3.6111111
t= 36

it will take 36 seconds for the car to catch to truck



the second question is simple

if it takes 2.9 seconds for the ball to hit then hear, the first part of the time is the bowling balls speed, and the second part is the sounds speed.

calculate sound first.

t = d/s
t= 16/340
t=.0471

therefore it takes the ball (2.9 - .047) 2.853 seconds to hit the pins.

calculate the speed of the ball

s= d/t
s= 16/2.853
s= 5.608

therefore the ball travels at 5.608 m/s




i think that your problem may be trying to solve the question straight away. take all the information from the question and write it down. then work out what you can from it, like the time for the speed of sound or the difference in speed of the cars. hope i helped
 
Back
Top