Question

It takes Priti 4 hours to drive from Ashdown to Bridgeton at an average speed of 50 mph. She then drives 30 miles from Bridgeton to Carton at an average speed of 40 mph. Assuming Priti doesn't stop, what is her average speed from Ashdown to Carton to 1 dp?

Answer 1

Her average speed from Ashdown to Carton is approximately 48.4 mph

Explanation:

The time and speed of the motion of Priti are as follows;

The time it takes Priti to drive from Ashdown to Bridgeton, t₁ = 4 hours

The average speed she drove from Ashdown to Bridgeton = 50 mph

The distance she drove from Bridgeton to Carton, d₂ = 30 miles

Her average speed from Bridgeton to Carton = 40 mph

The distance from Ashdown to Bridgeton, d₁ = 50 mph × 4 hours = 200 miles

The time it takes Priti to drive from Bridgeton to Carton, t₂ = 30 miles/(40 mph) = 0.75 hour

Average velocity,
`v_(ave)` = (Total distance traveled, Δd)/(Total time, Δt)

Δd = d₁ + d₂, Δt = t₁ + t₂

Δd = 200 miles + 30 miles = 230 miles

Δt = 4 hours + 0.75 hour = 4.75 hours

∴ The average velocity,
`v_(ave)` = (230 miles)/(4.75 hours)

∴
`v_(ave)` = (920/19) mph

Her average speed from Ashdown to Carton, rouded to 1 d,p,
`v_(ave)` ≈ 48.4 mph