The temperature, T° Celsius, of an object, t minutes after it is removed from a heat source, is given by T = 55e⁻⁰·¹ᵗ + 15.
- (i)Find the temperature of the object at the instant it is removed from the heat source.[1]
- (ii)Find the temperature of the object when t = 8.[1]
- (iii)Find the value of t when T = 25.[3]
- (iv)Find the rate of change of T when t = 16.[3]
Mark scheme
Marking points from the official mark scheme (May/June 2011). The mark or mark type is shown in brackets.
- [1] (i) 70
- [1] (ii) 39.7
- [1] (iii) 55e⁻⁰·¹ᵗ = 10 oe
- [1] (iii) 0.1t = ln(55/10) oe
- [1] (iii) 17(.0)
- [1] (iv) dT/dt = -5.5e⁻⁰·¹ᵗ
- [1] (iv) -5.5 (for k value)
- [1] (iv) -1.11
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